Take Control of Your Apple Wi-Fi Network (1.2)

Covers 802.11ac and 802.11n

Glenn Fleishman

This book is for sale at http://leanpub.com/tco-your-apple-wi-fi-network

This version was published on 2015-11-20

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© 2014 - 2015 Glenn Fleishman

ISBN for EPUB version: 9781615424382

ISBN for MOBI version: 9781615424382

Read Me First

Welcome to Take Control of Your Apple Wi-Fi Network, version 1.2, published in November 2015 by TidBITS Publishing Inc. This book was written by Glenn Fleishman and edited by Tonya Engst.

Make your Apple wireless network fast, reliable, and secure. Learn to configure the 802.11n and 802.11ac AirPort Extreme and Time Capsule and the 802.11n AirPort Express. Plus, get directions for setting up complex networks, adding shared printers and disks, and connecting to your network from OS X, iOS, Windows, Android, and Chrome OS.

This book focuses on Apple Wi-Fi networking in late 2015 with up-to-date software. In many cases, my advice works with older software and in some cases I give specific information about older software. In general, the older your operating system, the less likely you’ll find that everything works as described.

If you want to share this ebook with a friend, we ask that you do so as you would with a physical book: “lend” it for a quick look, but ask your friend to buy a copy for careful reading or reference.

Copyright © 2015 Glenn Fleishman. All rights reserved.

Updates and More

You can access extras related to this book on the Web (use the link in Ebook Extras, near the end; it’s available only to purchasers). On the ebook’s Take Control Extras page, you can:

Download any available new version of the ebook for free, or buy any subsequent edition at a discount.

Download various formats, including PDF, EPUB, and Mobipocket. (Learn about reading on mobile devices on our Device Advice page.)

Read the ebook’s blog. You may find new tips or information, as well as a link to an author interview.

If you bought this ebook from the Take Control Web site, it has been added to your account, where you can download it in other formats and access any future updates. However, if you bought this ebook elsewhere, you can add it to your account manually; see Ebook Extras.

Basics

Here are a few rules of the road that will help you read this book:

Read Me First: To review background information that might help you understand this book better, such as finding System Preferences and working with menus on the menu bar, read Tonya Engst’s free ebook Read Me First: A Take Control Crash Course, available for free on the Web or as a standalone ebook in PDF, EPUB, and the Kindle’s Mobipocket format.

Links: All blue text in this book is hot, meaning you can click (or tap) it, just like a link on the Web. If you click a link that takes you to a different part of the book, you can return quickly to where you were if your ebook reader offers a “back” feature. For example, if you use iBooks to read the EPUB of this book, you can click the “Back to” link at the lower left. Or, if you use Preview on the Mac to read the PDF of this book, you can choose Go > Back or press Command-[.

Finding the Wi-Fi Menu

The Wi-Fi status menu appears near the right of the menu bar on a Mac. Its icon normally looks like a fan (Figure 1). If yours isn’t showing, you can turn it on via a checkbox in the Network system preference pane, in the Wi-Fi view.

[picture]

Figure 1: The Wi-Fi status menu appears in the set of icons at the right of the menu bar.

If you see a different fan icon marking your menu, read Mac Wi-Fi Iconography to learn what that icon means.

What’s New in Version 1.2

The motivation for this update was to add information about iOS 9, 10.11 El Capitan, and Windows 10. Along the way, I found a few other details that I wanted to add or change:

I found two great tools for graphically mapping Wi-Fi networks and for visualizing a network environment—NetSpot and WiFi Explorer—so I added a run-through of each product in Testing from Client to Base Station.

I’ve made several small revisions about 802.11ac waves. Previously, when I discussed the latest flavor of Wi-Fi, 802.11ac, it was as a single thing; however, the standard is being rolled out progressively in waves, each with new features. Apple’s two 802.11ac base stations and nearly all the adapters in Macs and iOS devices currently use wave 1. The iPhone 6S and 6S Plus support wave 2, and I expect that Apple’s next flagship base station hardware revision will add wave 2 support.

In case you want to adjust or prioritize the way a Mac makes network connections in different locations—and be able to choose a location quickly—I added more detail in Manage Network Locations.

I added a sidebar, Wi-Fi Assist Boosts Wonky WLAN, that describes iOS 9’s new Wi-Fi Assist feature, which is enabled by default. Because this feature can burn through cellular data, iOS 9 users should keep it on only if they are aware of this risk.

I added steps for connecting to an Apple Wi-Fi network from Android and Chrome OS in Connect in Android and Connect in Chrome OS.

Because you may want to buy a base station without paying a premium for an Apple product—or you may want to try a different feature set than what Apple is currently offering—I added the sidebar Two Non-Apple Router Options That May Suit You to draw your attention to a few models that are worth a look.

What Was New in Version 1.0 and 1.1

Version 1.0 of this book was a new edition of a title that has been available in various iterations for over a decade. Version 1.0 focused on Apple’s 802.11ac gear and on 10.9 Mavericks, iOS 7, and Windows 8.1.

Version 1.1 added details for 10.10 Yosemite and iOS 8 as well as information about how to Connect with a Personal Hotspot and Share with AirDrop. This version also described new behavior in the hidden Wi-Fi menu, in Use the Wi-Fi Menu, and had various changes because the outdated WEP security option is finally gone; in particular, see Wait, Where’s WEP?!.

Finding an Old Edition

For help with an older version of Mac OS X, iOS, or Windows, older base station gear, or an older version of AirPort Utility, you can refer to a previous edition of this ebook—there’s no extra charge. Follow the “access extras” link in Ebook Extras, and look in the blog.

Introduction

It’s never been easier in Apple’s 16-year history of offering wireless networking equipment to set up a Wi-Fi base station and start working. But if that’s so, why read a book on the topic?

Even though setup is much, much easier than ever—especially with more powerful and sophisticated radio gear in the base stations—so many of the fine details of creating a network that does precisely what you want still require carefully plotted, step-by-step procedures. This is especially the case for networks with multiple base stations, attached disks, and sensible encryption.

In this book, I provide you with tips to save time, improve security, extend range, and enjoy a technical edge when working with Wi-Fi.

I start with wireless basics, move through base station installation and configuration, explain how to share printers and disks, tell you how to connect to a Wi-Fi network, give advice on extending a network’s range and quality, look at using an AirPort Express’s unique features, and finish with how-to information on security for those who want their AirPort networks safe from freeloaders and intruders.

Apple Wi-Fi Quick Start

Use this Quick Start to get an idea of how you might jump into the book if you are at a particular stage in working with your network.

Tip: Trying to solve a problem? Flip ahead a few pages to the Quick Troubleshooting Guide or see Light Reading to learn what the light on your base station is trying to say. Also, see Overcome Interference.

Learn wireless basics:

Get a quick grounding in Learn Wireless Basics.

Familiarize yourself with Wi-Fi Gear from Apple.

Plan your network:

For common configurations, see Picture Your Scenario and focus on the diagrams and descriptions at the beginning of: New Network, Single Base Station, Extend a Network via Ethernet or Wi-Fi, and Replace an Existing Base Station.

For ideas on using the AirPort Express, skim AirPort Express Extras.

For advanced possibilities, consult Connect Multiple Base Stations and pay special attention to the descriptions and diagrams at the start of Add Access Points via Ethernet and Bridge Wirelessly. Also, note that Appendix B covers creating a Software Base Station and Ad Hoc Networking.

Although it’s not necessary for a basic setup, you can consider your network’s channels and bands in Spectrum Trade-offs.

Set up your base station(s):

You’ll be using AirPort Utility to configure your base station. Read Meet AirPort Utility to learn the basics.

Unpack your base station and start down the path of configuring it inMeet AirPort Utility.

Share a printer or a hard drive. See Set Up a Shared Printer or Set Up a Shared USB Disk.

Set up Time Machine backups with an AirPort Extreme or Time Capsule in Work with Time Machine.

Connect to your base station:

Find out how to connect Macs, iOS devices, Windows systems, Android systems, and Chrome OS devices to a base station in Connect Your Devices.

Reach Your Network Remotely when you’re not physically on it.

Access your base station with the Back to My Mac service in iCloud. See Access a Base Station via iCloud.

Add audio:

Stream audio (and video) through AirPlay. See Stream Audio with AirPlay and Share with Airfoil.

Connect between devices:

Tether your Mac, iOS device, or other device to a cellular connection when you Connect with a Personal Hotspot, including using iOS and OS X with Instant Hotspot.

Try AirDrop peer-to-peer file transfer in Share Files with AirDrop.

Secure your network:

Avoid Simple Tricks That Don’t Work.

Apply encryption using the best—and often simplest—method. See Use Built-in Encryption.

Let visitors and friends in, when you Set Up Guest Networking.

Learn still more advanced topics:

Stop pulling your hair out over a problem with new firmware you install that doesn’t work. See Reverting to Older Firmware.

Get a few details about saving and re-using an AirPort base station’s settings in Appendix A: Configuration Files.

Quick Troubleshooting Guide

If you need quick help, here’s the starting point. I first look at handling a locked-up base station and then give tips for solving common problems, including problems with Personal Hotspot on an iOS device.

Note: Light Reading, a few pages ahead, helps you learn about a problem by decoding a base station’s LED status light.

Resetting a Locked-up Base Station

If an AirPort Extreme, AirPort Express, or Time Capsule appears neither in the Wi-Fi menu as an available network nor in AirPort Utility as an available base station, or AirPort Utility identifies it as missing, try these steps in order:

Check for a Local Connection

Make sure that the computer running AirPort Utility is on the same local network as the base station. Try connecting the computer via Ethernet to a LAN port on the base station. Try AirPort Utility again.

Cycle the Power

If a direct Ethernet connection doesn’t work, try cutting the power to the base station.

Before you turn off a Time Capsule, make sure Time Machine backups or other transfers aren’t in progress—for each computer on the network that uses the Time Capsule, eject any mounted Time Capsule volumes and halt Time Machine backups. The easiest way is via the Time Machine system preference pane: flip On to Off. After you power cycle the Time Capsule, you can flip Time Machine back on for each computer.

Remove the plug from the wall socket or remove the end that plugs in to the base station. Wait 10 seconds. Plug the base station back in, and see if it appears in AirPort Utility. Everything may be back to normal.

Reset the Base Station

If the above two options don’t work, then try a reset.

A hard reset will erase any custom settings you’ve made, but if all goes well, you’ll be able to restore them. Straighten an end of a paperclip, and with the base station plugged in to power, hold down the base station’s reset button with the paperclip tip for about 5 seconds until the status light turns amber and flashes rapidly. Release the button and wait a minute or so for the base station to restart.

The reset button is found in different places on each model:

2013 AirPort Extreme and Time Capsule: The reset button is to the right of the power jack and has a gray triangle printed on it (Figure 2, left).

[picture]

Figure 2: Left: On a 2013 model, a gray triangle is printed on the itty-bitty reset button, which I circled in red here. Right: On a 2007–2012 model, the reset button is located below the reversed-out white triangle; here it’s shown above the audio port of an AirPort Express.

2012 AirPort Express: The reset button is above the audio jack (Figure 2, above right).

2007–2012 AirPort Extreme and Time Capsule: The reset button is recessed at the rear right. The reset label, a white triangle reversed out of a gray circle, is above the button.

The base station boots in a factory-default state. The sidebar below has directions for restoring your settings.

If the hard reset didn’t work, try a factory reset, as described in the sidebar below.

Three Kinds of Reset

Apple has an extremely detailed FAQ about base station resets that’s worth reading if you have problems. The crucial thing to know is that there are three kinds of resets on all 802.11n and 802.11ac base stations:

Soft reset: Hold reset for 1 second, and the base station disables passwords and network security for 5 minutes, during which time you may change settings, including passwords. AirPort Utility indicates that the device is in a “soft reset” state, and its LED flashes amber. After 5 minutes, if you’ve made no changes, it re-enables passwords and network security.

Hard reset: Hold reset for 5 seconds, and the base station flashes its LED rapidly in amber, and then restarts. While it boots up in a clean, factory-default state, it also stores your previous settings. To restore those settings, click Other Wi-Fi Devices in AirPort Utility (at the upper left of the main AirPort Utility for Mac screen), click Other Options, select Restore Previous Settings, and then click Next on subsequent screens.

Factory reset: Unplug the base station’s power cord, and then hold in the reset button while you plug it back in. Keep the reset button depressed until the LED flashes rapidly in amber, which Apple says should happen after about 6 seconds. Your previous configuration is lost, and the base station is returned to the state in which you bought it. (Apple updated its directions for a factory reset in March 2015, which may reflect a firmware change. Before that with modern base stations, you could perform a factory reset on a crashed base station by holding the reset button for 5 seconds or longer while it was still powered up.)

Arrange for a Repair

If none of the above helps…

Call Apple for return instructions if the unit is under warranty. If not, it may be time to invest in a new one.

Tip: If you buy a Mac and add Apple’s extended-service plan, AppleCare, the plan covers any base station you purchased up to 2 years before the Mac and during the entire 3-year extended-warranty period of AppleCare. (AppleCare counts from the date of purchase of the Mac, though you have up to a year after that date to add AppleCare.) The base station comes with a 1-year warranty; AppleCare for Mac can expand that warranty to as many as 5 years for free repair or replacement for manufacturing defects!

Wi-Fi Network Won’t Assign IP Address

When connecting a Mac to a Wi-Fi network, you may sometimes see the oscillating waves in the Wi-Fi menu icon continue for several seconds, and then resolve with an exclamation point in a dimmed-out icon: . That means that although the Mac’s Wi-Fi radio could make a physical connection to the network, negotiating wireless standards, the underlying logical network server never responded to the computer’s request to assign an IP address to access the local network and, by extension, the Internet. To correct the problem, try the following fixes:

Run Network Diagnostics

From the Wi-Fi menu, choose Alert: No Internet Connection. Or, open the Network system preference pane and click Assist Me at the bottom. Follow the steps provided.

Renew the DHCP Lease

If Network Diagnostics isn’t helpful, try renewing the DHCP lease:

Open the Network system preference pane.

Select your Wi-Fi adapter in the list at the left. At the right, you should see a message about how the IP address is either missing or begins with 169, a so-called self-assigned address that a Mac may use when a network doesn’t provide one.

Click the Advanced button, and then the TCP/IP button.

Click the Renew DHCP Lease button. This signals the network’s DHCP server that you want an address.

Now, if the IPv4 Address field contains a legitimate address and you can access the Internet, you’re done. (You may have to revisit this, because a flaky network often doesn’t heal itself that fast.)

Try Another Solution

If after renewing the DCHCP lease the IPv4 Address field remains empty or it fills with an address starting with 169, try another solution…

Typical reasons why a network doesn’t assign an address boil down to misconfiguration, capacity, and distance:

Misconfiguration: A network may be set up incorrectly and nothing you can do will mitigate the problem. But, a router in a café or a back-end DHCP server on a large conference center network may simply need to be rebooted. Find the staffer or the “help” number for the network to see if you can get them to take action. (I’ve had to ask baristas to restart routers more times than I can recall.)

Capacity: Poorly configured networks may run out of network addresses to assign over Wi-Fi. This happened particularly often when the iPhone first shipped, because networks set to handle, say, 50 computers were suddenly inundated with dozens of iPhones. You can’t solve this problem on your end. You need a router or server to be restarted or even reconfigured.

Distance: Your Mac may appear to see and connect to a Wi-Fi network, but fail to get an address because it is at the edge of a usable signal and can’t reliably exchange network traffic. Try moving closer, using the tips in Testing from Client to Base Station for measuring signal strength.

Device Can’t See Base Station Network

Devices can sometimes temporarily lose their capability to find Wi-Fi networks—and don’t ask me why! (Or ask me, and I’ll shrug my shoulders.) It’s a mystery of many years. Sometimes a firmware or software update for a given piece of hardware causes Wi-Fi flakiness; read up on message boards for your product to see if there are general problems or general solutions.

Note: A friend once queried me about a problem with his network where his older base station seemed fine (its LED was green; it showed up on the Ethernet network), but the Wi-Fi network was unavailable. He eventually found that its power adapter brick was buzzing loudly. Replacing the brick solved the problem!

What commonly and frustratingly works is toggling the adapter off and back on:

On a Mac: From the Wi-Fi menu, choose Turn Wi-Fi Off, and then choose Turn Wi-Fi On (see Finding the Wi-Fi Menu). Another common fix is to restart the computer.

In iOS: Swipe up to get the Control Center, and then tap the Wi-Fi icon. Wait a moment; then tap it again.

Personal Hotspot Not Working

Personal Hotspot can be finicky at times on iOS devices. Here are the most common problems you’ll encounter—and some solutions:

Personal hotspot doesn’t appear as an available Wi-Fi network. Personal Hotspot enables Wi-Fi discovery for only a few minutes after you tap the feature on—sometimes it doesn’t enable it at all, for reasons I’ve never been able to diagnose. If you don’t see the network, tap the Personal Hotspot switch to turn the feature off and then tap again to turn it back on. The device should now appear in the Wi-Fi network list.

iOS device isn’t available for use as a personal hotspot. The Instant Hotspot feature makes an iOS device capable of serving as a personal hotspot appear, but only several conditions are met, documented in the sidebar Instant Hotspot Requirements.

No network connection after plugging in via USB. Check the Network preference pane and make sure there’s a USB iPhone entry in the adapters list. See Tether with USB in OS X, in Connect to a Personal Hotspot, for more problem solving advice.

Other Troubleshooting

Error occurs after connecting to a base station with the correct encryption key

You might be using a Mac with the older AirPort Card with a base station set up with WPA2 encryption. See Turn On WPA/WPA2 or WPA2 Personal.

Firmware update makes base station act erratically

Try to Reverting to Older Firmware.

Network works erratically

Another network might be interfering with yours. See Overcome Interference.

Mac Wi-Fi Iconography

The Wi-Fi menu—located on the system menu bar—reveals what kind of connection is in progress on your computer. Knowing what the icons mean can help you troubleshoot problems. This icon is always at the top of the Wi-Fi menu.

Note: If you don’t see a Wi-Fi menu on the system menu bar, read Finding the Wi-Fi Menu, earlier.

A gray fan indicates an active Wi-Fi network adapter that isn’t currently connected to a network. Read Connect Your Devices.

A full fan with one or more black bars—the bars represent current strength—indicates a current Wi-Fi connection to either a base station or a network created through the Sharing system preference pane’s Internet Sharing service. (An animation of each wave turning black in turn occurs while the connection is underway.) For more information, consult Connect Your Devicesand Appendix B: Setting up a Software Base Station.

iOS devices may share a cellular connection via Wi-Fi using the Personal Hotspot feature. When a Mac connects to such a network, the fan icon is overlaid with interlinked loops. Apple also uses this symbol in iOS to indicate a tethered connection of this kind.

A fan showing an up arrow indicates that the Internet Sharing service is active on this computer. See Software Base Station.

A fan containing a computer shows that the Mac has created an ad hoc network, a method of handling Wi-Fi communication among multiple computers without a base station—not even the “software” base station that’s created by Internet Sharing. See Ad Hoc Networking, in Appendix C.

A fan containing an exclamation point indicates an error in setting up the network part of the Wi-Fi connection. Although the computer has connected wirelessly to the base station, it was unable to obtain a network address. See Wi-Fi Network Won’t Assign IP Address.

An empty fan outline indicates that either there’s no Wi-Fi adapter in the computer or the Wi-Fi adapter is off. To turn it on, choose Turn Wi-Fi On from the menu. If the Wi-Fi icon still looks like an empty fan or an error says there’s no card or it can’t be turned on, you may have a hardware problem.

When you use the Network preference pane’s adapter settings (via its gear menu) to disable the Wi-Fi adapter, this X-in-a-fan appears to let you know that’s where you need to go to turn Wi-Fi back on. See Manage Network Locations.

The Eye of Sauron appears in its unblinking form that sees all and knows all when you use a monitoring mode in Wireless Diagnostics, a hidden tool that can help you sort through problems. See Run Wireless Diagnostics for more details.

Light Reading

The light on the front of any Apple Wi-Fi base station indicates what the base station is up to: handling data correctly, hitting an error, or in a special mode. Starting with 10.11 El Capitan, AirPort Utility also shows these lights, including blinking lights, in the form of status dots. The guide below helps you decipher the meaning:

Off: There’s no power! If the base station is plugged in, check that the wall outlet is live. (Plug a lamp into the outlet to test.) If it’s live, try methodically disconnecting and reconnecting any plugs between the base station and the wall in order to determine whether the problem is a loose connection or a broken cable. It might even be a failed power supply, a common occurrence with base stations.

Blinking green: The light blinks or flashes green in two cases:

Startup: The light flashes green on and off for 1 second.

Reset: This happens after you press the recessed reset button for long enough to trigger a reset.

Solid green: The base station is configured correctly, has no updates available, and is connected to the Internet.

Solid amber: The base station is still powering up and hasn’t loaded all its settings and connected to the network.

Slowly blinking amber: This light has several meanings:

The base station has a configuration problem, has lost its network connection, or is suffering from another problem. Use AirPort Utility to troubleshoot the problem.

You just did a soft reset, and the base station is in the 5-minute period when its access and network passwords are disabled.

A Time Capsule may have a Disk Integrity problem.

Rapidly blinking amber: You just did a hard reset (or a factory reset). The base station is modifying its settings before it restarts.

Learn Wireless Basics

Let’s quickly run through some basics to set the stage for what follows.

Adapters and Access Points

Wi-Fi networks need two connected parts: a wireless adapter and an access point. The wireless adapter is part of a computing device (such as a desktop computer, tablet, or smartphone), while the access point connects both to wireless adapters and to a broader network, such as the Internet via a broadband modem. An access point that’s coupled with a router is called a wireless gateway; Apple calls its wireless gateway a base station.

Apple’s lineup of base stations includes the AirPort Extreme, the AirPort Express, and the Time Capsule. When I talk about “AirPort equipment,” I mean all Apple base stations, including Time Capsules.

An AirPort network is a Wi-Fi network with some Apple extras that may work only with Apple software—under Mac OS X or Windows—or in conjunction with other AirPort equipment. Examples of such features include streaming audio, certain forms of hard-drive file sharing, and base-station-to-base-station connections.

What’s Wi-Fi?

The name Wi-Fi is a certification guarantee for which the Wi-Fi Alliance trade group owns the rights and controls the testing. Wi-Fi doesn’t stand for anything—it’s a made-up name—but it loosely connotes wireless fidelity, in the sense of faithfulness: devices with Wi-Fi stamped on them work with other Wi-Fi devices following the same standards, or are faithful to one another.

The wireless adapter uses client software on the device to connect to a specific base station (or set of affiliated base stations) after a user selects the network name from a list or manually enters the network name. (For example, on the Mac, you can choose a network from the Wi-Fi menu in the menu bar and from the Wi-Fi view in the Network system preference pane.)

When a device’s wireless adapter connects—technically, associates—with a base station, the device can send data to and receive data from the base station. If the base station has encryption enabled, then the device must provide an encryption key before the base station allows the device access to any networks to which it connects. The key, which consists of a series of characters, needs to be provided exactly as it was entered on the base station, whether typed or tapped in or sent from a keychain in the operating system.

Once an adapter connects to a base station and the encryption key is accepted, the device’s operating system can carry out the next steps, such as automatically requesting an Internet protocol (IP) address using DHCP and sending data over the wireless network.

With newer adapters, a connection may be made directly to another device with peer-to-peer networking regardless of whether the adapter is connected to a regular Wi-Fi network. An example is AirDrop, an Apple-only version of a more general standard called Wi-Fi Direct (see Share Files with AirDrop).

Wi-Fi Spectrum

Wi-Fi networks use unlicensed spectrum, so called because regulatory agencies allow license-free use of those airwaves by everyone in a given country. In contrast, cellular telephone companies pay huge amounts for the exclusive geographic rights to certain frequencies.

Note: In some developing nations, inexpensive or free licenses are required for outdoor use but not indoor use, or by businesses but not individuals. In the United States, Australia, Japan, South Korea, and most of Europe, no licenses are required.

Spectrum bands—specified ranges of frequencies—are divided into smaller portions called channels, which allow many devices to use the same band within “hearing” distance of each other, ideally without too much frequency overlap. Because unlicensed bands are intended for broad use by individuals and businesses, there’s no guarantee that interference won’t reduce the speeds you can achieve.

The rule is that in these unlicensed bands, devices use extremely low signal power, but they must be quite robust in order to cope with lots of interference.

In the United States and in most countries, two bands are available for use, the 2.4 GHz (gigahertz) band and the 5 GHz band. The precise frequencies and channels vary enormously by country. (The 900 MHz [megahertz] band is also unlicensed in the United States, but it is not employed for wireless LANs. The 1.9 GHz band is used by newer home cordless telephones.)

Over the years, AirPort gear has taken three approaches to handling bands:

Simultaneous dual band: The AirPort Extreme and Time Capsule models released starting in 2009 can use both the 2.4 GHz band (with 802.11n in all cases) and the 5 GHz band (always with 802.11n, and additionally with 802.11ac, depending on the model).

The 2012 AirPort Express can use both the 2.4 and 5 GHz bands.

Dual band: All 2007 and 2008 Apple base stations with 802.11n can use either the 2.4 or the 5 GHz band, you must choose one and then restart the base station to have the change take effect.

One band only: Older AirPort equipment from 1999–2006 (802.11b and 802.11g) works only in the 2.4 GHz band.

For more on 2.4 and 5 GHz bands, see Spectrum Trade-offs.

Warning! Many manufacturers, including Apple, sell specific hardware for each country or regulatory domain in which they do business. Because laws vary, it’s crucial that you don’t take a base station from, say, the United States to France and turn it on. You could wind up facing fines and jail time.

Note: You can download a previous edition of this ebook at no cost to learn how to make older and newer AirPort equipment work together. See Ebook Extras (on the Take Control site, look for the book’s Blog).

Wi-Fi Standards and AirPort Hardware

Apple’s AirPort hardware has gone through many transformations since its 1999 introduction. AirPort gear uses Wi-Fi standards created by the IEEE, the Institute of Electrical and Electronics Engineers. The IEEE has groups that work on many kinds of standards. The 802 group handles local area networks (LANs), and a working group in that area, numbered 11, covers wireless LANs (WLANs). This is called the 802.11 Working Group.

Each successive update to the standard produced by the 802.11 group is lettered and defines a particular set of codified ideas:

802.11b: The original flavor of Wi-Fi from 1999.

802.11a: Created in 1999 alongside 802.11b, 802.11a was used widely only in businesses for specialized purposes. However, 802.11n and 802.11ac adapters can connect to 802.11a networks.

802.11g: Released in 2003, this somewhat faster version of Wi-Fi was coupled with a security improvement.

802.11n: Much faster than 802.11b and g, this version appeared widely in 2007.

802.11ac, wave 1: Faster than 802.11n, this version of Wi-Fi appeared in 2012 and first showed up in Apple’s equipment in 2013.

802.11ac, wave 2: This even faster flavor of 802.11ac started to appear in mid-2015, and Apple has added it to the iPhone 6S and 6S Plus.

Upcoming: 802.11ad

The IEEE has a newer standard on the horizon for personal area wireless networks: 802.11ad, which will use spectrum way up the dial at 60 GHz for rates as high as 7 Gbps over very short distances, such as within a room. Devices are planned that will incorporate 80211.ad alongside older 802.11n and 802.11ac in a single package.

The Wi-Fi Alliance, a trade group, builds tests based on the 802.11 standards. These tests allow the many makers of Wi-Fi equipment to ensure that all Wi-Fi gear, regardless of manufacturer, can communicate and carry out a common set of tasks in the same way.

Since the original AirPort, Apple has released four major versions of AirPort hardware, three of which were related to major revisions of the IEEE 802.11 standards. Every older version of 802.11 can be used with even the newest base station models, so long as the newer base station has a legacy or compatibility mode enabled. (The 802.11ac models cannot have legacy mode disabled!)

Multiple Antennas and Radios

The earlier Wi-Fi standards—802.11a, b, and g—supported just a single radio, and if a base station that implemented these standards had multiple antennas, the antennas helped spread a signal but were all carrying the same information.

Starting with 802.11n, base stations and adapters could have two or more radios and multiple antennas. Having more radios allows techniques that send signals farther. More radios also allows for multiple simultaneous data streams—each radio sending a unique set of data at once that bounces across slightly different paths through space in the same frequencies! 802.11ac added beamforming, which lets a router vary power among multiple antennas to shape each signal with the energy more closely focused on each separate device that is simultaneously connected, while also avoiding pushing a signal to devices that don’t need to receive the data.

Think of this like pool balls on a pool table. A sending base station is the equivalent of two pool players shooting a series of balls at the same time from the same place at different angles. Thus, the balls uniquely ricochet across the table (sometimes striking and passing through each other in a ghostly fashion) until they sink into different holes. And if you hit them just right, all the balls wind up in the same point on the table at the same time.

Each incoming signal is “heard” by two or more antennas, making it easier to pick up more distant transmissions and to tease out the wheat (data) from lots of chaff (other, interfering signals and background noise).

These techniques boosted 802.11n’s rates tenfold above its predecessor, and 802.11ac can be much faster. While it’s often hard to pin down real-world rates, 802.11n devices have a raw rate of 75 to 600 Mbps (megabits per second) in the most popular configurations, including the 2012 AirPort Express. All of the simultaneous dual-band 802.11n Apple base stations (AirPort Extreme and Time Capsule in 2008 and AirPort Express in 2012) can work over both 2.4 GHz and 5 GHz at once, meaning you could have a 225 Mbps connection over 2.4 GHz and a 450 Mbps connection over 5 GHz simultaneously!

The 802.11ac standard uses only the 5 GHz band, but 802.11ac routers include backward-compatible support for 802.11a, g, and n to make sure other devices can still connect. Apple’s initial version of 802.11ac has a raw top rate of 1.3 Gbps, although it rarely achieves that performance because of practical considerations; there may not be enough spectrum available or the client device may not be close enough. Some companies even combine both bands and advertise “1.9 Gbps” of throughput! (See Throughput for more detail.)

However, with an 802.11ac router swapped in place of an 802.11n router, you should generally see faster transfer rates, and areas that had dead, slow, or poor coverage should have improved reception.

There’s yet one more 802.11ac detail: the technology is being released in waves, with nearly everything released to date being in wave 1. Wave 2, which began to appear in devices in mid-2015, adds higher data transfer rates—up to 2.3 Gbps in a single band! Apple put a version of wave 2 in its iPhone 6S and 6S Plus, but at this writing, there haven’t yet been upgrades to Macs or base stations to take advantage of wave 2.

Note: If you’d like to know more about they whys and wherefores of wave 2, read Cisco’s 802.11ac Wave 2 FAQ.

Single-stream Radios

A form of 802.11n and 802.11ac called single stream uses one or two antennas and a single data stream, which limits a device to raw rates of 75 Mbps in 2.4 GHz (802.11n only) and 150, 300, 433, or 867 Mbps in 5 GHz, depending on the flavor of 802.11n or 802.11ac.

While these rates seems contrary to the advantages of 802.11n and ac, they are still a huge boost over 802.11g—from double to several times that data rate. While MIMO was available in 802.11n, the just-appearing 802.11ac wave 2 adds the further advantage of multiple-user MIMO (MU-MIMO), which sends separate data streams at the same time to devices that have fewer radios than the base station’s maximum number of streams. Thus, a four-radio 802.11ac wave 2 base station could simultaneously send data to two one-stream devices and one two-stream device. A similar 802.11n or 802.11ac wave 1 base station would have had to send to each in turn, which reduces throughput.

MU-MIMO takes advantage of beamforming, described above. So if four one-stream devices are receiving data at the same time, each radio shapes a beam that puts most of the signal power for that radio at the device to which it’s communicating, and away from the others.

Apple has included single-stream 802.11n in all iPhone models since 2010 (iPhone 4) and all iPod touch models since 2009 (4th-generation). The iPad has had single-stream 802.11n from its first model, and went MIMO with the iPad Air and iPad mini 2. The iPad, iPhone 5 and later, and 5th-generation iPod touch and later handle both 2.4 and 5 GHz networking. The iPad Air 2 added support for 802.11ac wave 1, as did the iPhone 6 and 6 Plus, and the 6th-generation iPod touch. The iPhone 6S and 6S Plus added 802.11ac wave 2 support.

Compatibility among 802.11 Flavors

While each 802.11 evolution brings unique elements to the table, all 802.11 versions designed for the same band can work together. Newer versions are designed to not trample on all older versions, and base stations can be set to allow all, some, or no backward compatibility.

This means that even with the latest 802.11ac hardware, you can still potentially connect to the base station from even the pokiest device from 1999!

Note: The most recent encryption standard, WPA2, was introduced in 2004, and many adapters from 2003 could be updated to use it. However, because 802.11n and 802.11ac require WPA2 encryption as a minimum, it’s generally the case that if encryption is enabled, an 802.11b or early 802.11g radio probably can’t connect. See WPA and WPA2 Background, later, for a few more details.

With Apple gear, for instance, the original AirPort handled just 802.11b, and the AirPort Extreme 2003 added 802.11g, which can talk to 802.11b devices with full support. Likewise, Apple’s 802.11n base stations handle the older 802.11a/b/g standards, and its 802.11ac models support all four previous standards.

Transfer speeds between a slower adapter and a faster base station running a different 802.11 standard can’t exceed the speed of the adapter while the adapter is communicating. If an 802.11n device is trying to use a network that can work at 802.11ac speeds, it slows the network during the time that it’s receiving or sending data by, more or less, talking and listening more slowly. But when an 802.11ac adapter interacts with a likewise 802.11ac base station, even with 802.11n devices on the network, the full 802.11ac speeds are available.

While most of the loss in throughput happens only while older devices are taking up airtime (and newer devices are cooling their heels), enabling backward compatibility shaves some speed off a network’s maximum throughput. This is because each packet of data begins with a special message—a preamble—that’s encoded at a backward compatible speed so the slowest devices can understand it.

Apple lets you turn off backward compatibility, as described in Compatibility, but only with its older 802.11n base stations and the current AirPort Express. However, because the 5 GHz band supports the faster n and ac flavors, it’s not a huge issue for modern base stations and modern adapters.

Wi-Fi Gear from Apple

A long history with Wi-Fi has led to three devices in Apple’s current lineup of base stations, each with a distinct set of features. Let’s look first at how Apple has chosen to work with 802.11n and 802.11ac, and then at Apple’s current AirPort Base Station Models and the options for Adapters in Current Apple Devices.

At the end of this chapter, you should better understand the gear that you have, or be in a better position to shop for new equipment.

When Will Apple Release a New Base Station Model?

Apple last updated its base stations in 2012 (Express) and 2013 (Extreme and Time Capsule), a surprisingly long while ago. Given Apple’s track record, it seems likely that they will release new models in early 2016. (If Apple does, I’ll write about that in this ebook’s Blog; see Ebook Extras.)

The most obvious change that could be rolled out is support for 802.11ac wave 2, which makes higher throughput available in 5 GHz and offers MU-MIMO (described earlier) for more efficient network connections with devices that have simpler Wi-Fi radios.

802.11n, 802.11ac, and Apple’s Choices

Apple has made distinct choices when implementing Wi-Fi, but all three of Apple’s current base station models can handle both the 2.4 GHz band and the 5 GHz band at the same time.

Note: Despite the AirPort Express being called an 802.11n base station and the 2013 models of the AirPort Extreme and Time Capsule’s being labeled 802.11ac, these are really “multi-protocol” devices. That is, the Express can handle a, b, g, and n in any combination; the 2013 Extreme and Time Capsule handle a, b, g, and n while also adding ac in the 5 GHz band.

For the 5 GHz band, Apple enables just 8 of the 23 possible channels in the United States for use in a base station. This is because of a compromise among the radio equipment industry, the military, the FCC, and various government agencies. This compromise protects 15 of the possible 23 channels so that base station signals don’t cause even the slightest interference with weather-sensing and military radar, but it also makes it more difficult to use those channels for home networks.

Apple has chosen not to support those 15 channels in its base stations. The company doesn’t think that they would be consistently available in a way that would be useful to most consumers and small offices using AirPort gear. However, the newer 802.11ac wave 2 standard might spur Apple to make these channels available because wave 2 can use as many as eight regular channels at one time.

Note: The adapters in a Mac can, in fact, connect to all the 23 legal channels in the United States. Some companies may deploy Wi-Fi networks using non-Apple base stations that allow the use of all 23 channels, as they’re more likely to be available inside buildings without hitting military and weather radar rules.

Note: In March 2014, the FCC voted to add another 100 MHz for unlicensed wireless use, about 5 channels’ worth, in the 5 GHz without the same sort of restrictions that have plagued the 15 channels noted above. However, it is almost certain that no existing 802.11ac or n hardware will work in that new band. We may be waiting for some time before those are available in practical terms.

Apple also chose to limit 802.11n’s wide channels to the 5 GHz band. Wide channels are an 802.11n feature that uses two adjacent channels at once—this doubles the raw bandwidth. Apple’s choice was an option under the Wi-Fi Alliance’s certification rules, but some vendors do offer wide channels in 2.4 GHz. In practice, 2.4 GHz wide channels don’t work well, because 802.11n devices tread lightly to avoid interfering with other networks. In a real-world situation, you would likely see an improved in throughput with 2.4 GHz wide channels only if no other Wi-Fi networks were nearby.

Even wider channels are possible in 802.11ac wave 1: the equivalent of four normal channels in 5 GHz (80 MHz of spectrum), the only band in which 802.11ac functions.

In 802.11ac wave 2, a wide channel can encompass as many as eight normal channels (160 MHz), and devices can use four channels in a row in one part of the 5 GHZ band and four in another. That should make it more likely that the full bandwidth could be used.

AirPort Base Station Models

Apple’s current base stations are the AirPort Extreme, a solid offering for home networks and small offices; the Time Capsule, a backup system that’s coupled with Extreme features; and the AirPort Express, a compact router with most of the AirPort Extreme’s features but portable enough for travel. I discuss each device in the pages ahead.

Field Guide to Base Stations

Within its 802.11n and ac line, Apple has kept the same name for six generations of AirPort Extreme, five generations of Time Capsule, and two generations of AirPort Express. The dates for the Extreme and Time Capsule generations were 2007 (Extreme only), 2008, early 2009, late 2009, second-quarter (June) 2011, and June 2013. The AirPort Express comes in 2008 and 2012 models.

In AirPort Utility, you can see a unit’s model information by clicking its name in the graphical view and then hovering over its name in the popover, holding down Option while double-clicking the base station, or selecting a base station and Option-clicking its Edit button.

AirPort Extreme

Over the years, Apple has enhanced the wide range of features now available in the AirPort Extreme:

Simultaneous dual-band networking: With two internal radio systems, the early 2013 and later models of the Extreme base station can operate a 2.4 GHz (802.11b/g/n) and a 5 GHz (802.11a/n/ac wave 1) network simultaneously and independently, allowing the fastest devices to connect to the best network.

Guest networking: Starting with the early 2009 Extreme, you can set up a separately named Guest Network in addition to the network that you normally access. This feature creates a virtual network that shares the same networking hardware, but broadcasts a unique name that appears in the Mac’s Wi-Fi menu and on any device where you select a Wi-Fi network by name. You can set separate security options, too. Guests who connect have no access to local network traffic or peripherals, like printers or file sharing.

Ethernet: The Extreme has four gigabit Ethernet ports, three for the LAN and one for the WAN (Figure 3).

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Figure 3: The three-quarter front view (left) and straight-on back view (right) of the 2013 AirPort Extreme Base Station. The back ports are, top to bottom, three LAN Ethernet, USB, WAN Ethernet, and power. The tiny reset button is to the right of the power jack.

Note: Why so tall, Paul? The 2013 AirPort Extreme has a few inches of empty air inside. Its form factor is identical to the Time Capsule, which fills that empty space with a hard drive. Apple claims the signal carries better with a “higher platform,” but I suspect it’s a desire to have a unified appearance.

Note: All four ports on an Extreme (or Time Capsule) can be used as switched LAN ports if the base station is set to bridging mode and is connected via Wi-Fi to another base station. In this mode, the Extreme just passes through traffic from the network to which it’s connected. See Passthrough and Bridging.

1.3 Gbps throughput: Starting with the June 2013 Extreme, it can pump out up to 1.3 Gbps of raw data via 802.11ac in the 5 GHz band by bonding four channels (80 MHz of channels) and sending three separate 433 Mbps spatial streams. In practice, this keeps data rates consistent over longer distances from the base station rather than providing overall faster throughput. In 2.4 GHz, the base station relies on 802.11n as its fastest flavor, topping out at 450 Mbps in a double-width channel.

USB: All Extreme models have a single USB port, which can be used to share a printer or hard drive across a network or the Internet; by attaching a powered USB hub, you can attach one or more printers or hard drives.

Power: AC power is supplied through a nearly 6.5 foot/2 meter long cable that plugs directly into the base station.

If You Need Speed

Gigabit Ethernet is far faster and simpler than Wi-Fi, with the only downside being the requirement for wires.

Ethernet switches can consistently deliver a few times the real throughput of 802.11ac between any two connected gigabit Ethernet devices in both directions. In contrast, Wi-Fi is limited to half its maximum speed when transmitting data between two Wi-Fi devices on the same network.

Time Capsule

The Time Capsule is a backup appliance with all the technical characteristics and external ports found in an AirPort Extreme base station, but with the addition of an internal 2 TB or 3 TB drive. It looks identical to an Extreme. Apple designed the Time Capsule to pair with the Mac’s Time Machine feature for making network backups. Any computer with 10.5 Leopard or later installed can back up files over Wi-Fi or Ethernet to a Time Machine’s internal drive or an externally connected drive.

Tip: In AirPort Utility, you can Erase the internal drive in a Time Capsule.

AirPort Express

Apple refreshed the Express completely in 2012, although it remains at 802.11n. The latest model is a puck, measuring 3.9 by 3.9 by 0.9 inch/98 by 98 by 23 mm and weighing 8.5 ounces/240 grams. It sports a 6.5-foot/2-meter long cord that plugs into an integral power supply.

The Express is quite similar to the AirPort Extreme, but with three exceptions and one important addition. The exceptions are:

The Express has two 10/100 Mbps Ethernet ports (one for WAN and one for LAN). The lack of gigabit Ethernet is a shame, because that puts a top end on the speed of 802.11n traffic that can pass between it and Ethernet. (Having just installed gigabit broadband at my home, I can say first-hand that this is a constraint!)

The Express has a USB port for sharing a single printer, but, unlike its two big brothers, it cannot share multiple printers nor even a single hard drive.

From a wireless throughput standpoint, the Express allows a maximum of 300 Mbps of raw speed in 5 GHz and half that in 2.4 GHz.

The Express has a unique extra that makes it a must-have network add-on for some people: audio output via AirPlay. The unit has a special mini-stereo port that allows both analog output and digital optical (Toslink) output, depending on the jack and cord you use to route audio from the Express to a stereo.

Its small size and low weight makes it perfect to tuck into a bag for a trip, where it can be plugged into Ethernet in a hotel room to share an Internet connection via Wi-Fi.

Two Non-Apple Router Options That May Suit You

While Apple’s Wi-Fi base stations may suit Mac and iOS users best, there are a lot of other routers on the market—so many that it can be utterly confusing to figure out what to buy, and that’s why a lot of people opt for Apple products.

Two routers you might consider have unique properties that make them stand out: one is much less expensive; the other has more features and may have better coverage at higher throughputs:

TP-Link AC1750: The TP-Link AC1750 (also known as the Archer C7) retails for about $100. It’s very similar in features to the AirPort Extreme: simultaneous dual-band, with 450 Mbps 802.11n in 2.4 GHz and 1.3 Gbps 802.11ac in 5 GHz; guest networking; a four-port gigabit Ethernet switch; and two USB 2.0 ports that can handle file and printer sharing. It even has an on-off switch! However, it requires configuration through a Web browser, and a bit of technical knowledge to sort through its options. Its price makes it a reasonable alternative. I purchased one to extend an existing network where I needed to replace an old AirPort Extreme with an 802.11ac router, but I didn’t need to pay twice as much for an 802.11ac AirPort Extreme, as I didn’t need those features.

Google OnHub: Google has released two OnHub models. These Wi-Fi routers are designed to be attractive enough to be put on display, rather than hidden out of sight, which reduces signal strength. Both models have a number of future-looking features, including support for Internet of Things standards like 802.15.4 and Weave, and Google claims that their sophisticated antennas will allow faster and more thorough coverage of a house than other routers. But each router has just a single gigabit Ethernet LAN port, and they feel overpriced for what they deliver—at $200 for the OnHub model manufactured by TP-Link and $220 for the one made by Asus.

Adapters in Current Apple Devices

All Mac models for sale at this writing have dual-band 802.11ac wave 1 built in, except for the 13-inch non-Retina MacBook Pro, which is stuck at 802.11n.

All currently available iPad models include dual-channel 802.11n and MIMO, but the iPad Air 2 and iPad Pro also include 802.11ac wave 1.

The iPhone 5c and 5s support 802.11n, while the iPhone 6 and 6 Plus add 802.11ac wave 1, and the iPhone 6S and 6S Plus support wave 2.

The sixth-generation iPod touch (July 2015) has 802.11ac wave 1.

Meet AirPort Utility

AirPort Utility is an app from Apple designed to help you configure your Apple base station—and apply any available firmware updates—and to troubleshoot certain network problems. Before you set up your base station, skim the information here about viewing your network, and then follow the advice about keeping up to date.

In this chapter, I talk about AirPort Utility 6 for Mac and AirPort Utility for iOS.

AirPort Utility 6 for Mac runs in 10.7.5 Lion and later. My directions for AirPort Utility should work identically in Lion and later, but they’ve been specifically tested in El Capitan using version 6.3.6. (See Finding an Old Edition, earlier, for more about AirPort Utility for Windows and older versions of AirPort Utility.)

AirPort Utility for iOS is at version 1.3.4 at this writing, and it runs in iOS 7 and later. (It hasn’t been updated since September 2014!)

Note: On a Mac, you can launch AirPort Utility from /Applications/Utilities. In iOS, first download AirPort Utility from the App Store (it’s free), and then tap its icon to launch it.

View Your Network

AirPort Utility uses a graphical display of your network’s topology, the interconnection among its networked parts, to show which base stations are available and their respective statuses.

For example, in Figure 4, AirPort Utility shows that AirPortage Bay is connected to the Internet, while Downstairs AirPort and Guest Room Apr2011 connect via AirPortage Bay for their network needs. (They look to AirPortage Bay for DHCP and NAT address handling.)

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Figure 4: AirPort Utility offers a graphic depiction of your network and its interconnections.

The topology represents Ethernet connections with solid lines and wireless connections with dotted lines (Figure 5).

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Figure 5: A solid line means an Ethernet hookup, while a dotted line indicates a Wi-Fi connection.

A green dot appears to the left of a correctly functioning base station and to the left of an active, happy Internet connection, as you can see in the figure above.

An amber dot indicates a problem (such as a dead Internet feed), and in more recent versions of AirPort Utility, that dot slowly flashes during restarts or other alert states, just as it does on the physical base station. A yellow warning triangle means a base station that was once available can’t be found (Figure 6).

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Figure 6: A yellow warning triangle indicates a missing base station; click the base station icon to see suggestions for fixing the problem.

Click a base station icon, and basic details are revealed, such as the base station’s name, IP address, and firmware revision (Figure 7).

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Figure 7: Tap or click a base station icon to reveal details.

You can get all that information in a more conventional dialog form by Option-clicking Edit or holding down Option and double-clicking the base station icon. A Summary pane appears (Figure 8), showing everything in the hover-to-view popover, plus many hidden elements.

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Figure 8: The hidden Summary pane provides an easier view into a base station’s characteristics, and a better way to dig into wireless client details.

Click Edit to configure the base station. (In the steps ahead, when I tell you to “edit your base station’s configuration,” simply click the base station icon and then click the Edit button.)

You can also tap the Internet icon, a globe familiar to Mac users from its use in the Finder, to show a few details about the connection to the larger Internet.

AirPort Utility Password Handling

AirPort Utility handles passwords differently in OS X and iOS. In OS X, if you leave Remember This Password in My Keychain selected when entering the password, it’s stored indefinitely. You can remove this password by launching Keychain Access (it’s stored in /Applications/Utilities/), searching for the base station’s name, selecting the password, and pressing the Delete key. With iCloud Keychain set up to sync, deleting the password here will delete it on all your OS X devices.

If you don’t have a record of your password elsewhere, make a note of it first! (If you do accidentally lose track of your password, see the instructions earlier in Reset the Base Station.)

You can also uncheck the “remember” box and enter it each time you launch AirPort Utility.

iOS AirPort Utility formerly retained your password forever after you entered it, but more recent versions of the utility store it only for what it treats like an active session. After a few minutes of your iOS device being on standby, you have to enter the password again to modify settings. Have your password handy—either in a password-storage app or by memorizing it—to gain access. AirPort Utility for iOS oddly won’t read the iCloud Keychain entry for a base station.

Keep Up to Date

If your copy of AirPort Utility isn’t up to date, you should update it now through the Mac or iOS App Store.

Once you’ve updated AirPort Utility, you should then work in AirPort Utility to update any base station firmware that is out of date:

On a Mac: Select your base station, and click Edit. If a firmware update is available, that information will appear in the status area (Figure 9). To update the firmware, click Update.

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Figure 9: Select your base station to view a popover that alerts you if an upgrade is needed.

In iOS: Tap the base station icon, tap Version, and then on the Firmware Update screen (Figure 10), tap Download and Install.

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Figure 10: AirPort Utility for iOS lets you apply firmware updates.

Reverting to Older Firmware

If a firmware update causes trouble with your network, and that has been known to happen, you can reload (revert to) a previous firmware release. In AirPort Utility for Mac, select your base station and Option-click the firmware number by the Version label. A pop-up menu appears, listing all the previous firmware available. Choose the release you want to install (typically the immediately previous version), and then click Continue.

Updating AirPort Utility on the Mac

The first time you run AirPort Utility for Mac, it asks if it should check for updates automatically. This separate update conduit makes it more likely that you will apply any security, stability, and compatibility upgrades that you might otherwise ignore for a while.

You can adjust how often updates are checked in AirPort Utility’s Preferences window (Figure 11).

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Figure 11: You can check for updates regularly—or not.

AirPort Utility’s update notification works whether or not AirPort Utility is launched.

Plug In Your Base Station and Get Started

Let’s get unpacking! This chapter focuses on plugging in your base station and on launching AirPort Utility, the program that modifies a base station’s settings.

(The next chapter, Set Up a Network, helps you determine which network type you want to use your base station with, and provides specific instructions for a streamlined setup.)

Unpack and Power Up

Unpack the base station to determine what you have and if you need any additional hardware:

Remove the base station from its box and check the parts: The box includes just a few necessary parts: the base station, a setup booklet, a booklet full of software licensing information (extraneous for users, but required), and an AC power cord.

Do you need an Ethernet cable? Configuring a base station may be simpler if you temporarily hook it to a computer or existing LAN with an Ethernet cable, instead of making a wireless connection, so consider an Ethernet connection for setup.

Also, in the likely case that you plan to connect the base station to a broadband router or other network, you will need at least one Ethernet cable (labeled Category 5E or Category 6 if you’re using gigabit Ethernet) in order to make that connection.

Is the power cord long enough? Plan to buy an extension cord if the included 6.5 foot/2 meter cord is too short for your purposes. The Extreme and Time Capsule work best level on a table or floor, where the top of the unit has an unobstructed line of sight to the rest of the room. If you can, don’t put it inside a cabinet or behind a computer. (For now, your goal is to plug the base station in where you can set it up, though you may wish to skip ahead and read Pick the Right Place before you continue.)

Now it’s time to power up. Plug your base station into an electrical outlet, and plug an Ethernet cable from your Mac into any of the three LAN Ethernet ports on the Time Capsule or Extreme, or the single LAN Ethernet port on the Express. You can also plug in a base station via Ethernet to a switch or base station on the network to which your computer or iOS device is connected. If you’d rather have mobility while configuring, you can set up via Wi-Fi, but you must reconnect after each time you change password or naming options.

In a neat addition, each Ethernet port on a base station has a tiny green LED that lights up when an Ethernet cable is connected to the port and a live connection is on the other end of the cable; the LED flashes to indicate activity (Figure 12).

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Figure 12: A very, very tiny green LED inset into the Ethernet port glows to show an active Ethernet connection and flashes on traffic.

Note: A green/amber LED on the front of the base station shows the status of the base station. Light Reading, earlier, has more about the front LED.

I recommend not connecting a base station via the WAN (Wide Area Network) port to a broadband modem or the rest of your network until you’ve carried out more of the setup, especially the very next part.

Connect to a New Base Station

The moment a new base station is powered on, whether you’ve connected it to your network with Ethernet or it is in radio vicinity of a device’s Wi-Fi receiver, AirPort Utility on the device recognizes the base station. You can start configuring the base station from the Mac’s menu bar, from AirPort Utility for Mac, or from an iOS device with AirPort Utility installed:

Mac menu bar: From the Wi-Fi menu, choose the base station below the gray label New AirPort Base Station; the type of base station is listed (Figure 13). (Even if the Mac is connected to an active Wi-Fi network, it finds the new base station and doesn’t drop the current connection.) AirPort Utility launches and opens a configuration setup dialog.

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Figure 13: The Wi-Fi menu reveals unconfigured base stations in the vicinity, even ones to which you’re not connected.

AirPort Utility for Mac: Launch AirPort Utility, and click the faint Other Wi-Fi Devices button at the upper left (Figure 14). Choose the base station from this menu. (If your Mac is connected to more than one kind of network, such as Ethernet and Wi-Fi, the menu lets you choose over which kind you want to look for base stations if yours doesn’t appear in the initial scan. The default is your highest-priority network—the one that appears above the others in the Network system preference pane’s adapters list.)

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Figure 14: AirPort Utility shows base stations in the vicinity that you can configure.

Note: The menu also shows any base stations that are configured with Back to My Mac through iCloud under the Remote AirPort Base Stations label (see Access a Base Station via iCloud).

iOS: Launch Settings, tap Wi-Fi, and choose the base station by type beneath Set Up New AirPort Base Station (Figure 15). iOS starts the AirPort Setup process.

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Figure 15: Unconfigured base stations are listed near the bottom of the Wi-Fi view.

Now you can proceed to one of the scenarios listed at the beginning of the next chapter.

Default Network Names

When you first power up any Apple base station, new or old, the gateway creates a Wi-Fi network named Apple Network 0033FF where 0033FF is replaced with the last six hexadecimal digits of the AirPort ID of the base station’s 2.4 GHz band wireless adapter. In AirPort Utility, the base station appears in the Other Wi-Fi Devices list as Base Station Name 003FF, with the appropriate model type, like AirPort Extreme, replacing Base Station Name.

The AirPort ID is a MAC (Media Access Control) address. Read Appendix D: What and Where Is a MAC Address? to learn more information about MAC addresses.

Set Up a Network

In this chapter, I look at scenarios: pairing the kind of network that you want with an explanation of how to use AirPort Utility for a basic configuration of that scenario. (At the end of this chapter, I talk about two special options, Create Separately Named 2.4 and 5 GHz Networks and Configure IPv6 Networking. Most people can skip these topics.)

The next chapter helps you tweak your selection of channels and determine exactly where to place your base station.

Placing a Base Station

If you haven’t figured out where best to put your new base station or stations, you may wish to skip ahead and read Pick the Right Place. Note that you can configure a base station first, and then relocate it, using advice in that section to find the optimal placement.

Picture Your Scenario

Pick a scenario and proceed as directed; each scenario begins with a diagram and explanation of the type of network and then gives steps.

Are you:

Setting up a new network with a single base station connected to a broadband modem? See New Network, Single Base Station.

Extending a network? See Extend a Network via Ethernet or Wi-Fi.

Replacing an existing base station with a new unit and want exactly the same settings? See Replace an Existing Base Station.

None of the above. If your scenario isn’t in this list, consult later sections in this book, which examine advanced options.

New Network, Single Base Station

In the simplest setup, where you have a single base station and are connecting it directly to a broadband modem (Figure 16), you can breeze through setup.

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Figure 16: A simple network connects a base station via a broadband modem to the Internet.

To configure a new base station to create a new Wi-Fi network:

On the Mac or in iOS, select the base station as described in Connect to a New Base Station, previous chapter.

AirPort Utility (or AirPort Setup in iOS) shows its progress while it gathers information (Figure 17).

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Figure 17: AirPort Utility for Mac gathers information.

Since there are no other base stations to which you’re connected, wait until you see “This base station type will create a network.” Then, click the Next button to get a screen where you can fill in the details about your new network (Figure 18, iOS) and (Figure 19, Mac).

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Figure 18: Name and protect the base station in iOS.

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Figure 19: Name and protect your base station on the Mac.

Fill in the details:

Network name: The base station broadcasts this name. It appears in Wi-Fi selection menus on devices and computers.

Base Station Name (Mac)/Device (iOS): Enter the Bonjour name that will identify the base station in AirPort Utility, as well as in the Finder sidebar if a disk will be associated with the base station.

Single password option: You can set different passwords for configuring a base station, disk access, and network access. With this box checked (or switch turned on, in iOS), one password works for all purposes. (I discuss the details in Turn On WPA/WPA2 or WPA2 Personal.)

Password and verify password: This password allows encrypted access to the network and prevents unwanted people from connecting to the base station and changing its settings.

Click Next.

If you haven’t plugged an Ethernet cable into your broadband modem and base station, AirPort Utility explains that you need to (Figure 20). If you see this screen (or a similar message in iOS), plug in your cable or check your connections and then click Next.

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Figure 20: Plug in your Ethernet cable if you haven’t already, or check your cabling.

AirPort Utility (or AirPort Setup, in iOS) completes the setup. It may suggest that you power cycle your broadband modem as in Figure 21; click Next to proceed. In my testing, I’ve found that setup can take a minute or two to finish.

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Figure 21: Apple provides some final advice on making sure your new network works as expected.

When the dialog says “Setup Complete,” click Done.

Note: You must reset a base station to factory defaults to go through the setup process described above again.

Now that you’ve configured your base station, you may want to add a printer, configure special settings, or add another base station. To consider your options, read Apple Wi-Fi Quick Start, earlier.

Extend a Network via Ethernet or Wi-Fi

If you already have a network in your home or office, you may simply want to plug in another base station to extends its range. You have two options—via Ethernet or via Wi-Fi:

Ethernet: The most reliable way uses Ethernet to connect the first base station with any subsequent base stations (Figure 22). The first base station must be connected to the Internet, but the rest can connect via that base station for Internet access. Each base station should be given a unique name, but the network name is the same for all of them.

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Figure 22: Ethernet lets you connect a number of base stations together to form one seamless network across a home or office.

This method allows all base-station-to-base-station communication to happen over Ethernet. The adapter in any Wi-Fi device on the network automatically picks up and switches to the strongest network signal it can spot among base stations set up with the same network name.

You will likely connect a cable from the Wide Area Network (WAN) port on the new base station you’re adding to any of the three Local Area Network (LAN) jacks (Extreme and Time Capsule) or to the one LAN jack (Express) on the main base station.

Wi-Fi: You can opt to connect base stations wirelessly. With a wireless connection, base stations communicate with each other via Wi-Fi instead of Ethernet (Figure 23).

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Figure 23: Extending via Wi-Fi lets you avoid running a cable.

Note: With an 802.11n AirPort Express, you can extend any Wi-Fi network, using Apple equipment or otherwise, through a special, lightly documented mode called ProxySTA. See Connect to Any Base Station.

You can mix and match Ethernet and Wi-Fi network extensions, too. If you aren’t sure how you want to extend your network, think you have an unusual situation, or want to better understand the technical details, flip ahead to Connect Multiple Base Stations.

Note: The iOS version of the setup assistant is quite similar; to avoid replication, I’m not including the screen captures and steps here.

To extend your network with Ethernet or Wi-Fi in AirPort Utility, follow these steps:

Connect to the base station using a method noted in Connect to a New Base Station, such as clicking the Other Wi-Fi Devices button at the upper left of AirPort Utility.

AirPort Utility should recognize that the base station has been connected to an existing network and suggest how to configure the base station in that context (Figure 24).

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Figure 24: AirPort Utility helpfully suggests how to extend your existing network with the new base station.

Enter a base station name if you don’t like the one filled in for you, and click Next.

AirPort Utility connects to the new base station, configures it to extend your existing network, and restarts the base station. You will see a series of status messages as this progresses.

When you see “Setup Complete,” click the Done button.

Now that you’ve extended your network, you may want to add printers, configure special network settings, or add more base stations. For a road map to your options, see Apple Wi-Fi Quick Start.

Replace an Existing Base Station

This option lets you replace an Apple base station (or a non-Apple router) that’s already in use or that was in use on your network. For instance, you might be replacing a single-band-at-a-time 802.11n base station with a new 802.11ac unit (Figure 25). You can use the setup assistant to replace the base station in moments.

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Figure 25: You might want to replace an existing base station with a newer, faster one, without having to re-enter all of the current base station’s configuration details.

Tip: If you’re swapping in a wired base station, put your new base station near your old base station for ease of swapping cables.

Note: The iOS version of the setup assistant is quite similar; to avoid replication, I’m not including the screen captures and steps here.

Follow these steps:

Connect to the new base station using any method noted in Connect to a New Base Station, such as clicking the Other Wi-Fi Devices button at the upper left of AirPort Utility.

AirPort Utility will try to sort out the existing network and offer to let you extend the network. Instead, click the Other Options button.

Select Replace an Existing Device, and click Next (Figure 26).

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Figure 26: Select Replace an Existing Device to proceed.

AirPort Utility asks how to proceed (Figure 27).

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Figure 27: Pick the kind of router you’re replacing.

If you are replacing an AirPort base station, select An AirPort Base Station, and then click Next. Then, from the Wi-Fi Network pop-up menu (Figure 28), choose the network that contains the base station that you want to replace. Click Next.

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Figure 28: Pick the network that contains the base station that you want to replace.

From the Base Station to Replace pop-up menu (Figure 29), choose the base station that you want to replace (if you can’t figure out the correct name and don’t want to interrupt this sequence, use AirPort Utility on another device). Name the new base station something descriptive, and click Next.

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Figure 29: Pick the base station to replace.

If you want to replace a router that is not an Apple base station, click Next. Then, follow the directions shown in AirPort Utility for how to attach the new Apple base station in your existing network, and click Next (Figure 30). Click Done. (See Replace an Existing Base Station, earlier.)

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Figure 30: Use this guide to swap in your new Apple device.

AirPort Utility connects to the new base station, configures it to extend your existing network, and restarts the base station. You’ll see a series of status messages as this progresses.

When you see the message “Setup Complete,” click the Done button.

Replacing a Base Station and DHCP

When you start up a base station with an identical configuration as the one you replaced, computers that use DHCP to obtain an address from the base station might not know about the new base station and thus might not be able to communicate with it.

If a Mac can’t access the Internet, open its Network system preference pane, select the Wi-Fi or Ethernet adapter (whichever is connected), click Advanced, and click the TCP/IP button. Click Renew DHCP Lease, and wait for the number to go away and re-appear. Click OK, and then click Apply.

Also, note that the range of internal IP addresses that the base station’s DHCP server assigns to your local computers may now be different; see Hand Out LAN Addresses.

Now that you’ve set up your base station, you may want to add printers, configure special settings, or add more base stations. For a road map to the options, go back to Apple Wi-Fi Quick Start.

How to Return to the Factory Defaults

You can reset any Apple base station to its factory settings at any time through software or hardware. Resetting the base station loses all settings you’ve applied, including passwords. If you save a configuration (see Appendix A: Configuration Files), you can load that configuration after resetting the base station.

To return to the factory defaults using AirPort Utility:

On a Mac: Select your base station, click the Edit button, and then choose Base Station > Restore Default Settings. Click Continue in the dialog that appears, and wait for the base station to restart.

In iOS: Tap the base station, tap Edit, tap Advanced, and slide down to see the Restore Defaults button. Tap it, and then confirm by tapping Restore in the alert box that appears.

If you can’t connect to the base station or prefer to use a hardware approach, see Reset the Base Station for the steps for using the built-in reset button.

Create Separately Named 2.4 and 5 GHz Networks

Apple’s simultaneous dual-band base stations are designed to a let a Wi-Fi client pick the best network at any given time, so by default both networks must use the same name. OS X has been optimized to balance speed and range in choosing a given band’s network, so it monitors a network connection for when the signal becomes marginal in 5 GHz, or for a 2.4 GHz connection, for when a 5 GHz signal is strong enough to swap over to. But in some cases, you might want your network to act as though it were two separate networks, locking some Wi-Fi devices to one network to avoid them flipping back and forth.

Note: The 5 GHz band should always provides faster networking than the 2.4 GHz band unless a client device is very far from the base station, but still in range of the 2.4 GHz signals it sends. Also note that 802.11b or g devices can’t communicate over the 5 GHz band, while the 802.11ac standard works only over 5 GHz. Read Spectrum Trade-offs for details.

The limitation with a separately named 5 GHz network is that it must share all the settings of the 2.4 GHz network, such as encryption method, DHCP, and so forth.

Apple has buried this option slightly; here’s how you access it:

Make sure your new base station is prepped as explained in Connect to a New Base Station.

Edit the base station’s configuration.

If you’re working on a Mac, click the Wireless button and then click the Wireless Options button. In the Wireless Options dialog (Figure 31), select the 5GHz Network Name checkbox and enter a different name than the name shown in the main Wireless view.

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Figure 31: The 5 GHz network name should be different than the Wireless Network Name entered in the Wireless pane.

Click Save and then Click Update.

If you’re working on an iOS device, tap Advanced > Wi-Fi Settings and then tap the 5GHz Name field. Enter a name for the 5 GHz network. It should be different from the network name in the main view for your device (Figure 32).

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Figure 32: Name the 5 GHz network separately.

Tap Done repeatedly to reverse through a few configuration screens, and then tap Update.

Configure IPv6 Networking

The next generation of Internet routing, the way in which data from one device finds its way across the Internet to another device, has the moniker IPv6. That’s Internet Protocol version 6 as compared to what we’ve been using for most of the Internet’s history, version 4 (IPv4).

IPv6 is necessary because the IPv4 system has run out of addresses to assign to computers and devices. IPv6 has vastly more available numbers to hand out, and it is the Internet’s inevitable future. Mac OS X, Windows for many versions, iOS, and other operating systems have built-in support for the longer addresses in IPv6.

After over a decade of not quite making it all work, the Internet’s various standards bodies, companies, and network providers have finally started to make IPv6 viable.

Note: By default, Apple has IPv6 networking enabled and set to Automatic, as noted in Step 2 below.

Warning! You shouldn’t touch these settings unless you like to experiment and know what you’re doing, or your ISP has provided precise information for a particular purpose that you agree with.

Follow these steps to configure IPv6 in AirPort Utility 6.1 and later:

Select your base station and click Edit; then click the Internet button and click Internet Options.

Choose an option from the Configure IPV6 pop-up menu:

Link-Local Only: This setting works only for a LAN, and doesn’t try to pass IPv6 back and forth to the Internet. (If you’re concerned for some reason about inbound IPv6 connections, set your router to Link-Local Only, and IPv6 traffic cannot be routed to the Internet.)

Automatically: Choose this option in order to pick up whatever settings are provided by your ISP, if any. This is the default option, and you likely can leave it alone.

Manually: If you pick this option, you’ll next need to enter the base station’s assigned IPv6 address and the IPv6 address for the router that provides Internet access.

Choose an option from the IPv6 Mode pop-up menu:

Native: Pick Native to tell your base station to assume that the network supports IPv6 directly. That is the default, and should, again, almost certainly be left alone.

Tunnel: Choose Tunnel to wrap IPv6 within an IPv4 tunnel that will extend beyond your ISP’s local network to reach a valid IPv6 segment further out on the Internet. (If that doesn’t make sense, you probably didn’t need to know it, so don’t worry.) Tunnel works with the Automatically or Manually options available in the previous step.

For the most part, IPv6 doesn’t offer any specific benefits to end users, although it should ultimately make it easier to reach devices on local networks without having to punch through NAT (see Reach Your Network Remotely).

Comcast supports IPv6 pretty thoroughly, and I’ve found that with a passthrough broadband modem—one that bridges Comcast’s network to mine—setting IPv6 to Automatically and Tunnel pulls in an IPv6 address and sets up the routing (Figure 33).

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Figure 33: AirPort Utility sets up your IPv6 connection through Comcast’s tunnel.

Then any device that connects to the network that also supports IPv6, which is pretty much all modern desktop and mobile operating systems, gets its own IPv6 assignment as well (Figure 34).

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Figure 34: In OS X, the Wi-Fi network connection retrieves an IPv6 address via the base station.

Pick the Right Place and the Right Channel

This chapter helps you tune your network for optimum performance. It starts by helping you understand more about the portion of the radio frequency spectrum that your base station uses and how to determine the right channel to use in each frequency band. After that it explains how to Pick Compatibility and Set a Channel.

Finally, you’ll learn how to Pick the Right Place for a base station with General Testing Advice as well as details on Testing from Client to Base Station and Testing from Base Station to Client.

Note: Apple added simultaneous dual-band radios to the early 2009 Extreme and Time Capsule and the 2012 Express.

Spectrum Trade-offs

Shortly, I explain how to select channels for a base station. To make the best choice, you may need some background on spectrum and channel choices. (If you don’t know the basics of spectrum bands and channels, read Wi-Fi Spectrum before proceeding here.)

Let’s begin by comparing the two bands. The 2.4 GHz band is crowded with Wi-Fi networks, Bluetooth devices, and other uses; the 5 GHz band is relatively empty—in the United States, the band has almost seven times the amount of frequency available in 2.4 GHz. Further, Apple restricts what were once called wide channels to the 5 GHz band in 802.11n in order to avoid treading on 2.4 GHz networks. These broader channels in 802.11n use twice the amount of spectrum (40 MHz) and thus can achieve twice the data throughput.

802.11ac, which functions only in the 5 GHz band, can employ quadruple-wide channels of 80 MHz (wave 1) and octuple-wide channels that span 160 MHz (wave 2) of spectrum. These extra widths allow for substantial, almost linear increases in throughput

Other Uses of the 2.4 and 5 GHz Bands

The 2.4 GHz and 5 GHz bands weren’t empty before Wi-Fi networking came along. 2.4 GHz is known as a “junk band” because it’s full of approved uses that can conflict at times. Industrial sealers, for instance, use heating processes that emit 2.4 GHz radiation. (There are many other junk bands, too, most not used for networking.)

Problems with Wi-Fi networks often stem from your own or your neighbors’ use of conflicting technology, including 2.4 GHz cordless phones, microwave ovens, nearby industrial sites, and wireless cameras. The 5 GHz band has many fewer approved uses; primarily, 5.8 GHz cordless phones will be your enemy.

Throughput

The 5 GHz band offers consistent throughput—the amount of actual data passing over the network exclusive of overhead used to transmit it. With 2.4 GHz, however, throughput is all over the place. When other technologies interfere in the 2.4 GHz band, Wi-Fi devices and base stations are forced to slow down.

The highest possible 802.11n rate happens when two adapters use the 5 GHz band with 40 MHz, and the highest 802.11ac wave 1 rate happens with 80 MHz channels. (Apple doesn’t offer 802.11ac wave 2 base stations at this writing, so 80 MHz is as wide as you can go.)

Note: The highest rate for 802.11n is 150 Mbps in a wide channel times the number of streams in that band. That’s a minimum of 150 Mbps for single-stream devices up to a maximum of 600 Mbps for four-stream devices. With 802.11ac wave 1, it’s a minimum of 433 Mbps when an 80 MHz channel is available, and up to 1.3 Gbps in an Apple device. It could be much faster in future wave 2 devices, which could use 160 MHz and four streams for 2.3 Gbps!

Compatibility

An 802.11b or 802.11g device—such as an 802.11g Mac—can’t connect to a 5 GHz network, which is a reason Apple offers both 2.4 GHz and 5 GHz on its base stations. (Apple has never sold a device that can connect only in the 5 GHz band.) A visitor with an older adapter would be out of luck if a base station offered only a 5 GHz connection, as would anyone having a pre-2012 iPhone or iPod touch, or an older smartphone.

Note: Even in 2015, I’ve noticed that many inexpensive devices from other hardware makers use only 2.4 GHz in order to lower the cost. In preparing for this book, I purchased an entry-level Android phone (the Moto G) and an HP Stream 11 laptop with Windows 10 preinstalled. Both offer only 2.4 GHz networking with 802.11b/g/n.

Channels

Now that you understand the limits of the bands over which your base station broadcasts, it’s time to consider which channels to use.

2.4 GHz

For the 2.4 GHz band, when an Apple base station is set to Automatic, it does a great job in selecting a channel that’s as free of competing uses as possible. In some cases, you may want to set a specific 2.4 GHz channel in order to interleave channel usage on multiple base stations that you’re setting up, or because you know about particular problems in a given channel that you want to always avoid.

The 2.4 GHz channels are numbered 1 to 14, although just 1 to 11 are available in the United States. Channels 1, 6, and 11 are typically chosen in the United States because they lack any real overlap with each other. In countries in which 14 channels are available, 1, 6, 10, and 14 may be used with little overlap. (The 2.4 GHz channels are staggered, meaning any two adjacent channels share about 75 percent of the same frequencies; 1, 6, and 11 are mostly clear of each other.)

Note: There are many myths about channels. When I had a network installed recently by the local phone company, a remote tech support person said that I absolutely needed to set the 2.4 GHz network to channel 10. There is no reason why that advice should be given in the United States; I was perfectly polite but went ahead and chose a different channel after I was off the call.

5 GHz

The 5 GHz band in the United States has a bigger trade-off: Apple makes 8 out of 23 possible channels available: 36, 40, 44, and 48 in the lower set, and 149, 153, 157, and 161 in the upper set. (The 5 GHz channel mapping doesn’t overlap, with each regular channel having a full 20 MHz width.)

The lower set is limited by U.S. regulators to use 1/20th, or 5 percent, of the signal strength allowed in the upper band. More power usually means greater range. If you use Automatic to set the 5 GHz channel choice, Apple’s firmware always picks an upper-band channel, unless it senses interference in all the available choices and opts for a lower-band channel to make sure the network will work.

You may want to set a specific channel in 5 GHz to ensure that you’re always using the full available power for the best range. Or, you might want to set a low-numbered channel to avoid blasting your 5 GHz network around the neighborhood.

The 5 GHz band is much less available in most other countries, some of which allow a small slice of 4.9 GHz spectrum to be used instead.

Note: To learn more about how channels work, read Appendix C: Channels Explained.

Pick Compatibility and Set a Channel

You can configure a base station’s band, compatibility, and channel in AirPort Utility.

Set the Radio Mode (802.11n Only)

Radio Mode has to do with which 802.11 standards a base station uses, so by setting the Radio Mode you set the band and compatibility all at once.

Note: The 802.11ac base stations automatically make every 802.11 standard available; you don’t get a choice.

If a base station is a wireless extension of a network, it must have the same settings as the base station connected to a broadband modem or larger network.

Otherwise, you can pick which 802.11 standards a base station will use with AirPort Utility, though it’s handled differently in AirPort Utility for Mac and AirPort Utility for iOS. (AirPort Utility for Mac offers more options, though you probably don’t need them.)

I first explain how to find the Radio Mode controls in AirPort Utility for Mac and AirPort Utility for iOS, and then I help you with Picking Radio Mode Options (802.11n only) in a sidebar.

Set the Radio Mode in AirPort Utility for Mac

In AirPort Utility for Mac, edit your base station and click the Wireless button, and then the Wireless Options button. In the Wireless Options dialog, choose an option from the Radio Mode pop-up menu, which—if you press Option while opening the menu—offers a multitude of choices in every combination (Figure 35).

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Figure 35: When you configure a simultaneous, dual-band base station in AirPort Utility for Mac, press Option while opening the Radio Mode pop-up menu to see a long list of choices, as shown here. Or, don’t press Option and see just the top three choices. You’ll see fewer options for a one-band-at-a-time base station.

Set the Radio Mode in AirPort Utility for iOS

In AirPort Utility for iOS, edit your base station and then tap Advanced > Wi-Fi Settings > Radio Mode to open the Radio Mode screen (Figure 36). In the Radio Mode screen, turn off Automatic to enable the 5GHz Mode and 2.4GHz Mode options, and then tap the option you want.

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Figure 36: To view the Radio Mode screen, edit your base station and then tap Advanced > Wi-Fi Settings > Radio Mode.

On the 5GHz Mode screen, you can pick just 802.11n (with 802.11a compatibility) or 802.11n only operation (Figure 37).

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Figure 37: The 5GHz Mode screen provides two choices.

The 2.4GHz Mode screen offers just two options: 802.11n with 802.11b/g compatibility or 802.11n only (Figure 38).

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Figure 38: The Radio Mode screen lets you choose from two major options for the 2.4 GHz band.

If you need a greater range of options, use AirPort Utility for Mac.

Picking Radio Mode Options (802.11n only)

You’ve found the place in AirPort Utility where you can set the Radio Mode, but which option is right for you? Here’s the run down:

Automatic: This default menu option on the Mac and On/Off switch in iOS works with a simultaneous dual-band base station to provide full compatibility with different types of 802.11 devices: 802.11a/n in 5 GHz, and 802.11b/g/n in 2.4 GHz.

802.11a/n: This option gives full backward compatibility in 5 GHz, allowing older Intel devices without 802.11n to connect at better ranges and speeds. Choose “802.11a/n – 802.11b/g/n (Automatic)” or “802.11a/n – 802.11b/g” on a Mac, or tap “802.11n (802.11a compatible)” in the 5GHz Mode view in iOS.

802.11b/g/n: This option is fully backward compatible in 2.4 GHz. Choose “802.11a/n – 802.11b/g/n (Automatic)” on a Mac, or tap “802.11n (802.11b/g compatible)” in 2.4GHz Mode view in iOS.

802.11a, 802.11b, 802.11g only, 802.11b/g (Mac only): These modes, available as menu items in combination with other modes, lock out various other modes and are for compatibility only. The only reason to use one is to set up WEP, an older form of security that provides no protection. On a network with 802.11n, WEP can be used only in a deprecated and broken form called Transitional.

802.11n only (5 GHz), 802.11n only (2.4 GHz): These modes disable the special backward-compatible preamble that transmits at the slowest speed, removing overhead and disabling adapters that can’t talk 802.11n from the band.

Set the Channel (All Models)

The channel selection options let you choose channels in one or both bands depending on your base station model. AirPort Utility defaults to Automatic for both bands, where the base station picks a channel based on which channel has the least amount of radio activity:

On a Mac: In the Wireless Options dialog (edit your base station, click Wireless, click Wireless Options), choose any channel listed in the 2.4GHz Channel or 5GHz Channel pop-up menu.

In iOS: In the Radio Channel view (edit your base station, tap Advanced > Wi-Fi Settings > Radio Channel) turn off the Automatic Channel switch for either band (or both), and then tap the band’s channel label to select a fixed channel.

Pick the Right Place

Now that you’ve chosen a band and channel, it’s time to find the right spot to put the base station. I have a pile of advice for how to place your gateway in your home or office. In testing, you might need to change the band or channel, even!

When you walk around with a cell phone, the number of bars showing signal strength varies, depending on the strength of signals received from nearby cellular network transmitters. It’s the same situation over a much smaller space when you connect a computer to a Wi-Fi gateway. Depending on where you place the base station, its signal may or may or not penetrate with enough strength to be useful.

When you position your base station, consider these factors:

Does your broadband modem hookup constrain where you locate your base station? Many of us have phone or cable connections in non-ideal locations for locating a Wi-Fi gateway. You might turn to powerline networking (see Extending with HomePlug) or even run an Ethernet cable through the walls in order to put your base station far from your broadband modem.

Where do you want Wi-Fi connectivity? Do you want to work in your backyard? Upstairs and downstairs?

What obstacles might block your signal? Walls, ceiling, floors, and even metal exercise bikes can all absorb and reflect Wi-Fi signals, reducing their range and quality.

2.4 and 5 GHz networks have different ranges at the same output power. Can you get the faster 5 GHz signals where you need them but have the coverage of the 2.4 GHz network for the rest of the area in which you want service?

Pick a spot near the middle of where you want your signal to reach and test if it’s a good location for your base station. Make sure the top part of an 802.11ac base station isn’t obstructed: it should have a clear line of sight around it, and not be in a cabinet or behind a computer.

You want to get the best average signal in all the places from which you want to connect. To run the test, just power up the base station: its default settings provide a name and a signal.

General Testing Advice

Here are some general tips for finding your ideal location:

Leave the base station in one place while you try all the areas you want to use it in.

Spend up to 30 seconds in a spot to see if the signal strength varies. (The next few pages explain how to check the signal strength.)

Use sticky notes to mark signal strengths at the locations where you want to provide wireless network access. Write down each location and the signal strength that you see there so it’s easy to determine the ideal placement of the base station later.

All three devices have omnidirectional antennas—ones that send and receive in all directions. However, they are optimized to create a signal pattern that spreads outward from their narrowest sides to better fill a room. The best orientation for a base station is with its feet flat on a surface.

Note: All flavors of Wi-Fi work at speeds below their maximum rates as an adapter becomes more distant from the access point.

Testing from Client to Base Station

There are several ways you can test how well a client can interact with a base station:

To test the connection between a single Mac and the base station, use the data in the Wi-Fi menu (described just below) or Run Wireless Diagnostics, a utility that comes with OS X.

Try the slightly hidden Wi-Fi scanner option in the iOS AirPort Utility app. See Scan with AirPort Utility in iOS.

To monitor all the base stations and networks in your vicinity, refer to Plot with NetSpot and Measure with WiFi Explorer.

Use the Wi-Fi Menu

The Wi-Fi menu in the menu bar offers connection information that is useful for troubleshooting (Figure 39).

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Figure 39: The Wi-Fi menu displays signal information.

Hold down the Option key and open the menu to get answers to several key questions about your currently connected network:

Is my Internet connection active? If so, what is the router’s IP address and the IP address assigned to this computer? (New in Yosemite)

How am I connected to the router?

Security method (such as WPA2 Personal)

The router’s BSSID, the equivalent of a MAC address

PHY Mode, the protocol in use, like 802.11n or 802.11ac

Which channel is use (including the frequency band), as well as which country’s regulatory structure is used on the base station

MCS Index, a very technical value relating to a combination of factors that make up the current connection’s data rate and encoding

How well can my computer receive the base station’s signal? The RSSI (Received Signal Strength Indicator) measures in decibels how well a signal is being received. A higher number (closer to zero) means a stronger signal. You also can see a visual indication of signal strength by observing the number of black waves in the symbol at the far right of each network’s name. New in Yosemite, the Noise value is also shown.

How fast is my network running? For a network that you’re currently connected to, you see the Tx Rate, or transmit rate, which indicates how “fast” the network is operating. Apple’s 802.11ac in the Time Capsule and AirPort Extreme can operate at a raw rate of up to 1.3 Gbps (in 5 GHz) or 225 Mbps (in 2.4 GHz); for example, in Figure 39 (above), for the Portage Airbasestation, the rate is 867 Mbps using 5 GHz channel 149.

Bandwidth information (20 MHz, 40 MHz, or 80 MHz), first appeared in the Channel item in Yosemite. The bandwidth relates to the maximum speed, while the transmit rate can change constantly, as the adapter and base station negotiate for faster or slower connections as problems are encountered.

You can also Option-click the Wi-Fi menu and then hover over any network, not just the one selected, to receive a few useful details (Figure 40).

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Figure 40: You can get details about networks to which you’re not connected, too.

Run Wireless Diagnostics

To access Wireless Diagnostics, hold down the Option key while opening the Wi-Fi menu on the menu bar and then choose Open Wireless Diagnostics from near the top. (If you’ve used this utility before Yosemite, it’s changed from the version you might be familiar with. Apple has overhauled Wireless Diagnostics four times by my count across three OS X releases.)

The utility prompts you to click Continue so it can start to collect data that you can send to Apple to help with troubleshooting, but instead you can proceed with another part of the program that lets you monitor your network from a laptop while walking around. You can also use Wireless Diagnostics to view the results of relocating your base station.

Choose Window > Performance and a constantly updated view of the connection from the Mac to the base station appears, as in Figure 41.

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Figure 41: Monitor the quality of a connection to a base station with Wireless Diagnostics.

Performance shows three separate charts over time, with the newest data coming in from the right and pushing the older data to the left:

Rate: At the top, you see the raw data rate in megabits per second; the figure above shows 867 Mbps.

Quality: The middle chart displays a quality measurement, which is actually the SNR or signal-to-noise ratio. The signal contains information, while the noise prevents that information from being received; the ratio of the two corresponds to the current potential throughput of the connection. The ratio, measured in decibels (dB) tells you relative quality. The threshold starts at about 10 dB, below which there’s no connection, and changes to well above 40 dB, which is the best quality. In the graph shown above, you see how terrific the connection is, because it’s well above 40 dB.

Signal: The Signal chart, at the bottom of the Performance window, shows the raw signal (green; labeled RSSI, which stands for Received Signal Strength Indicator) and noise (blue) values. The signal is best the closer that the green line is to the top and the blue line is to the bottom.

Note: Apple did something cute with the Wi-Fi menu bar icon in another of the Wireless Diagnostics utilities. Choose Window > Sniffer and click Start. The icon changes to a very amusing “all-seeing eye.” Click Stop, and it reverts to its usual appearance.

Scan with AirPort Utility in iOS

Although iOS doesn’t offer a way to monitor Wi-Fi with ongoing graphing as in OS X’s Wireless Diagnostics, the iOS AirPort Utility app has a hidden Wi-Fi scanner mode that you might not even know exists. To make it available, tap Settings and then swipe down to AirPort Utility. Tap AirPort Utility and turn on the Wi-Fi Scanner switch. Now in the app, you see Wi-Fi Scan at the upper right.

Tap that button, and you see a screen with Done and Scan buttons and a Scan Duration slider. Slide the scanner to set the duration, or just tap Scan with it set to Continuous and tap Stop when you have enough results (Figure 42).

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Figure 42: The utility produces a scan with limited but useful information.

The resulting scan shows only the RSSI measurement, which can be useful as a raw indicator, as well as the name, MAC address, and channel for each access point found. Tap the info button to see a list of channels that have base stations active. This list can be helpful for picking the right channel for a new base station (Figure 43).

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Figure 43: The scan offers a summary of which channels are in use near by.

Plot with NetSpot

Figuring out how well your base station (or stations) cover an area can involve a lot of walking around and looking at numbers. There’s an alternative: NetSpot. It takes just a few minutes with this Wi-Fi mapping program to create a rich, interactive graphical visualization of where signals reach and how strong they are.

Start using NetSpot on its Survey pane. You can import a house or office plan, sketch one, use a sample map, or start with an empty page. You measure the distance between two points you mark on the map and it uses that to scale the rest of the map. Then you wander around the premises with a laptop, clicking to measure at various points (Figure 44).

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Figure 44: To begin, you click a number of points on the map.

You can mark just a handful of sampling points, but I like to use many for greater insight. Once you’ve finished sampling, you have an interactive map. One of the absolute neatest features of NetSpot, and one reason I was immediately impressed with it, is that it can accurately calculate where your access points are located (Figure 45).

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Figure 45: NetSpot creates a heat map of access based on measurements at the points you clicked.

In my survey above, I have an 802.11ac AirPort Extreme on our main floor, and then a single-band-at-a-time 802.11n AirPort Extreme in the basement near my desk. At the other end of the house, in a guest room, I have an 802.11n AirPort Express. The upstairs base station was placed within several inches. The downstairs units, sampled through the floor, were only a few inches further off.

The interactive map lets you select and deselect base stations in a list, so you can see in isolation and together what your best coverage is. The spectrum of colors ranges from blue (terrible) through cyan to green (good) through yellow to red (best). This provides a lot of granularity at a glance, if you can remember that green, yellow, and red are good, better, best. You can also open the pop-up menu found at the lower right to toggle what’s overlaid on the map as a whole (Figure 46).

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Figure 46: You can pick what appears on the overlay.

The free version lets you visualize only up to five access points at once, which includes each radio on a multi-band router. I have three routers, two of which are simultaneous dual-band models, and thus I was able to see my whole network within the five-unit limit. In addition, the free version is intended for non-commercial use with personal computers.

For offices, NetSpot Pro costs $149 for a single-user license, and the ten-user NetSpot Enterprise license is $499. These prices are reasonable if you’re maintaining multiple large networks, and you get a lot more features to boot.

Once you have a completed map, print it out to use as a guide, so you can consider improvements while you use WiFi Explorer, discussed next, to measure and analyze both the signals in the air and the radio choices you and your neighbors have made.

Measure with WiFi Explorer

WiFi Explorer ($15) provides a continuous scan with information about signal and noise for all the 2.4 and 5 GHz networks in your vicinity, including each base station in a multi-base station network.

WiFi Explorer helps tremendously with understanding interference from adjacent networks by providing both comprehensive details and graphical insight. It also lets you see at a glance precisely how your network is configured. Apple doesn’t offer that in AirPort Utility, which shows connections and base station names, but requires you to hover over each base station to see channel assignments and other details.

WiFi Explorer has just one window with four views at the bottom, three of them visualizations (Figure 47). When launched, the app starts scanning. If you don’t see updates, make sure the top display says “scanning.” The scan is updated every 5 seconds. A left navigation bar lets you filter networks discovered in the vicinity by Wi-Fi mode, network name, and other parameters.

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Figure 47: WiFi Explorer shows an enormous amount of detail in both list and visualization formats.

The list at the top is typical of Wi-Fi scanners, such as Apple’s Wireless Diagnostics, discussed above. WiFi Explorer packs a lot of information into a well-designed space. But click any entry, and the area below the list lights up (Figure 48). The app assigns a color to each base station in the list, which is useful in the visualizations.

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Figure 48: Select a base station name in the list and WiFi Explorer shows the full extended set of same-named networks.

The Network Details view shows a rundown of technical information specific to the selected base station, and at the left a continuously updated scan of network quality, which can be viewed as signal, signal and noise, or signal-to-noise ratio. At the right, the view shows a color-coded bar based on signal strength of all other base stations using the same Wi-Fi channel.

If multiple base stations use the same network name (or SSID, Service Set Identifier), selecting any one of them adds a display between signal strength and channel occupancy that shows each base station’s power on the same signal axis, split by frequency band (2.4 GHz and 5 GHz). You can hover over any bar and WiFi Explorer shows its individual base station name (Figure 49). Click any bar, whether in the middle or right display, and the base station is selected in the list at top. These collections of networks are shown under Service Set in the Results bar at left, too.

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Figure 49: Hover over a bar and its base station name appears.

You can see an overlay of all networks’ signal strengths by clicking the Signal Strength button (Figure 50). Selecting one or more items in the list fills in the color below the line in the graph to make them more visible.

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Figure 50: The Signal Strength view provides data over time for nearby networks.

Note that Signal Strength view doesn’t show network throughput, which would require software installed in different devices to check the link between them; this is just the capability of a Wi-Fi network to work within the parameters of a given network speed. The Max Rate column in the access point list shows the current data rate at which a device is operating. Access points drop through a large combination of modulations and channel uses between the lowest and highest data rates; the higher the data rate, the closer the computer running WiFi Explorer is to the base station while being unimpeded by other networks spreading signal over the same space.

The Channels view is remarkable (Figure 51). It shows how different base stations are occupying swaths of frequencies. In 2.4 GHz, you can see where networks overlap.

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Figure 51: The visualization lets you see the full signal and frequency overlap of networks in the vicinity.

The signal strength information is gathered over time, and clicking the stop button or quitting the app results in a prompt to save the results. The data is stored in a static snapshot that you can re-open in WiFi Explorer to review later, whether offline or to compare with current network environment details.

Testing from Base Station to Client

AirPort Utility once had a variety of diagnostic tools, but only a vestige remains. Now, you can pull up just a few hints:

On a Mac: Select a base station to see a list of any connected hardware beside the Wireless Clients label. Hover over, but do not click, any client name, and a floating panel appears (Figure 52), showing connection details: the data rate, RSSI, and PHY mode, as described earlier in this section, in Use the Wi-Fi Menu. You can also see this information in AirPort Utility’s Summary pane by Option-clicking the Edit button.

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Figure 52: In AirPort Utility for Mac, the Wireless Clients entry shows connection information. Wow, that’s a lot of clients for a family of four in a small house!

Note: Bonjour names won’t show up on a network in which the main base station isn’t an Apple model, as the Bonjour messages aren’t always passed through with that extra name information.

In iOS: The same information that you can access in AirPort Utility for Mac is available in iOS, nested a few layers deep. Select a base station, then tap Wireless Clients (you may have to slide down), and then tap a client name. Then tap Connection to get the details on Data Rate, RSSI, and (PHY) Mode (Figure 53).

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Figure 53: AirPort Utility for iOS nests connection status a little deeper than the Mac version.

Advanced Networking

Did the simplified setups explained in Set Up a Network not cover everything you needed to get up and running? In this chapter, I spell out the details for connecting a base station to a WAN and for further configuring addressing on your LAN. Advanced options are needed for networks that use static or fixed addresses, and for anything the slightest bit unusual.

Note: If you’re building or re-building a network with more than one base station, read this chapter first to set up the base station that connects directly to your broadband service provider. Then read Connect Multiple Base Stations.

Note: To stream music to an AirPort Express with AirPlay, see AirPort Express Extras.

Get a WAN Address

The more complicated scenarios start with getting a WAN address for your base station; you’ll then move to LAN configuration.

To communicate with the rest of the world, you need to hook the wide area network (WAN) port of your base station either into a broadband modem or, if you have an existing Ethernet LAN to which you are connecting the base station, into that larger network (Figure 54).

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Figure 54: Plug your broadband modem into the base station’s WAN port.

Start with an Ethernet cable and plug it into the WAN port on your AirPort device. Connect the other end of the cable to the LAN port of your broadband modem, or to an Ethernet switch for a larger network.

LAN vs. WAN

Connecting a broadband modem to a LAN port will not connect it to the Internet. The WAN port (Figure 55, left) has a circle of gray dots above it; the LAN port (Figure 55, right) sports a dotted line with an arrow on either end.

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Figure 55: Left: the WAN port. Right: the LAN port.

When you make your Ethernet connection, be sure to plug the cable in to the correct port.

Now that you’ve made the physical connection, you can configure your base station to handle the connection. The many different possible configurations can be broken down into two categories: those that use dynamic addressing and those that use static addressing:

If your Internet connection is a home broadband connection, you’ll probably use dynamic addressing; you may need to ask your ISP for more information if you’re not sure whether they provide you with a dynamic address or not. For configuration details, read “Dynamic Addressing,” next.

A static address is more typical for small and large offices. For setup information, see Static Addressing, a few pages ahead.

Dynamic Addressing

A dynamic address is an Internet protocol (IP) address that is assigned through Dynamic Host Configuration Protocol (DHCP), a relatively old Internet technology. With DHCP, your base station requests an IP address via its WAN port, acting as a DHCP client. A DHCP server on the other end of the Internet connection (typically at your service provider) receives the request and provides an address. And that’s as complex as it has to be.

A dynamically assigned address can be a private address, one that’s restricted to the ISP’s own network; that network is hard for anyone to reach, making your network even more inaccessible. However, a dynamically assigned address could, instead, be a publicly routable address, which is part of the global numbering system for IP addresses.

To set up dynamic addressing for your base station, proceed as follows:

By default, Apple’s base stations obtain an IP address as a DHCP Client. In most cases, no additional steps are needed, as shown in Figure 56.

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Figure 56: By default, a base station is configured to use DHCP, which on most networks is the correct and simplest way to connect it to the Internet.

In some cases, you might need to enter the DNS (Domain Name Service) IP addresses manually, or you may choose to override ISP-provided values. DHCP server DNS addresses are shown in the DNS Server(s) fields in gray. In AirPort Utility for Mac, select your base station and click Edit, and then in the Internet view (Figure 56, above), you can click to type and replace them.

If you need to use PPPoE or have MAC address issues with configuration, then New Network, Single Base Station may not have answered all your questions; keep reading in this chapter to find out how to log in via PPPoE over Broadband DSL (just ahead) and Deal with MAC-Address-Restricted Cable Broadband.

Some ISPs require you to jump through more hoops to connect to their networks, such as by putting you through a login process or by restricting your access to a single computer. The former method is used mostly by DSL providers; the latter, by cable firms.

Log In via PPPoE over Broadband DSL or Fiber

For security and tracking purposes, many DSL and fiber providers require that you use PPPoE (PPP over Ethernet) when connecting to their network. With PPPoE, you log in with a username and password to your ISP over your DSL or fiber connection, at which time you are automatically assigned an IP address and the connection works just like any other broadband connection.

If you need PPPoE, configure it in the Internet pane of AirPort Utility for Mac by choosing PPPoE from the Connect Using pop-up menu (Figure 57).

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Figure 57: PPP over Ethernet connects with a login name and password.

Still on the Internet pane, click the Internet Options button to choose a connection option in the PPPoE Connection pop-up menu: Always On is the most likely choice.

Warning! Some ISPs won’t give you the PPPoE login information.

Deal with MAC-Address-Restricted Cable Broadband

To prevent multiple machines from accessing a single cable-modem connection, some providers restrict access to a single MAC address.

ISPs use two common methods to restrict access by MAC address:

In the less annoying method, the cable modem powers up and then locks on to the MAC address of the device that’s connected to it. You can switch between devices by unplugging and reconnecting the cable modem after you connect your base station.

In the more annoying method, you must register the MAC address with the ISP in some way, whether manually or through an automated system. You may need to call your cable provider—which may want to charge an additional monthly fee—to register the MAC address of your base station’s WAN port.

Note: To learn more about MAC addresses, read Appendix D: What and Where Is a MAC Address?.

Static Addressing

A static address is an IP address that is entered manually and is fixed over time. A static address could be private or public. To enter a static address, you need details provided either by your ISP or, for an office network, by a network administrator. You need:

The static IP address: This address could be from an internal private range or a public address reachable from the Internet.

The subnet mask: A number full of mystery, the subnet mask merely defines the size of the local network that the static address comes from, with “size” expressed as the number of addresses in that local range.

The router address or gateway: This is the address to which any outgoing traffic that’s not bound for other machines on the local network is sent, to be routed to higher-level networks, such as a larger office LAN or the Internet.

DNS server(s): You need the IP address for at least one DNS server, which handles turning domain names into IP addresses. Two is better; that avoids slowdowns if the first DNS server is unavailable or overloaded.

To configure static addressing, edit your base station in AirPort Utility for Mac, click the Internet button, choose Static from the Connect Using pop-up menu, and then enter the values (Figure 58).

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Figure 58: Configure the Internet connection manually by entering the static values provided by your ISP or network administrator.

Hand Out LAN Addresses

With the WAN link connected, it’s time to look at your own network—the LAN. The LAN can be configured to assign IP addresses to client computers in one of four ways:

Dynamic Private Addresses: In this common mode, the base station shares one incoming Internet address with all the machines on the LAN. The base station assigns addresses to computers on the LAN from a private range; you can modify that range. The addresses are typically transient for any given computer. The base station coordinates traffic between the LAN and the greater Internet so that all packets end up in the right place.

Dynamic Public Addresses: With this setup, the base station shares multiple, publicly routable Internet addresses with devices on the LAN.

Reserved Addresses: With this feature, you can assign specific private or public addresses to individual computers on the LAN.

Passthrough and Bridging: You can set up a base station to let another device on a larger network dynamically assign addresses or allow static addresses. With this set up, the base station doesn’t manage addressing.

The first option is by far the most common, in which devices on the LAN receive addresses that can change from time to time, and which exist solely to give the devices access to the Internet. The other options are typically used when computers on the LAN side of the network are providing services and need to be reached by devices on the Internet or by devices on another LAN to which your base station is connected.

Let’s look through each of these in turn.

Note: DHCP works by having a device send a message over a network asking for an address. A DHCP server hears this message and provides an address. The DHCP client pulls the address that the DHCP server provides.

Dynamic Private Addresses

As with the WAN side of the equation, if you set up your network using the straightforward assistant in AirPort Utility, you should have no changes to make, so you needn’t read further in this topic; you can skip ahead to Connect Your Devices. However, should you want to control which addresses are assigned or manage other details of NAT and DHCP, read on.

To configure the rest of the DHCP addresses for assignment and the duration of each assignment, carry out the following:

In AirPort Utility for Mac, edit your base station, click the Network button at the top of the dialog, and choose DHCP and NAT from the Router Mode pop-up menu.

Click Network Options.

In the DHCP Lease field (Figure 59), you can set the length of a time of a DHCP lease, which is the association of a given computer with an address that’s been handed out. You can opt to set units of time in minutes, hours, or days in the pop-up menu.

Tip: It’s worth setting the lease period only if many devices frequently use the network and you don’t want to “use up” all the addresses, which are taken out of the pool for the duration of the lease.

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Figure 59: The IPv4 DHCP Range controls comprises a pop-up menu for choosing one of three private address ranges, a field for setting the third number in the IP address, and fields for entering the start and end range of your addresses.

You can work with IPv4 DHCP Range pop-up menu and its associated fields to specify the numbers and range of addresses used for standard DHCP address assignment on your network.

The only reason to change the range of numbers is if you want to create and assign private addresses that remain static instead of being allotted arbitrarily from a large pool when a computer or device requests an address via DHCP. These statically assigned addresses would start with the first three numbers in the base station’s private network range, but you would enter them manually on each computer. This used to be the only way to create a fixed private address, but I now suggest you avoid this method by using Reserved Addresses, discussed later in this chapter.

DHCP addresses are drawn from one of three reserved ranges of private addresses: 10.0.*.*, 172.16.*.*, or 192.168.*.*. The * refers to a number in an appropriate range, typically 0 or 1 through 254 or 255. These prefixes are reserved by the global numbering authority, and they are guaranteed to not be in use on any public Internet network. You can choose any of these three starting points from the pop-up menu, although Apple uses the 10.0 prefix by default.

In the first field to the right of the pop-up menu, you can enter any number from 1 to 254. The prefix combined with this third IP number portion defines your network. If you choose 192.168 and enter 1 for the third number, your network is 192.168.1.*, where the star represents numbers that can be set on the local network for individual computers and other devices.

The fourth IP number piece you enter, in the second field to the right of the pop-up menu, defines the starting address for a range of DHCP addresses. Typically, you enter 2 here because the router reserves the *.*.*.1 address to itself.

Note: 2⁸-2!The lowest legitimate number in the fourth number position of an IP address is 1; the highest is 254; 0 and 255 have particular reserved network purposes.

The final number, following “to” is the end of the range. It may be from any number starting at or including the starting address number all the way to 254. Apple, by default, sets this field to 200. You might set this to a lower number if you have a complicated network. In most cases, you can leave the default setting in place.

Tip: You can set a static address for any device on the network without using DHCP at all as long as it falls outside the range. In OS X, for instance, in the Network system preference pane’s Advanced > TCP/IP view, you can chose Using DHCP with Manual Address. You then enter an address that isn’t within the range, like 192.168.1.201 if 200 is the highest number you set.

Click the Save button, and if you’re all done in the Network pane, click Update.

NAT (Network Address Translation) is handled in the bottom half of the Network Options dialog, which offers two settings relevant for remotely accessing programs running on one or more computers on the LAN. I discuss how NAT works and what these settings offer in Reach Your Network Remotely.

Note: I explain DHCP reservations in Reserved Addresses (ahead shortly), the options for port mapping in Map Ports for Remote Access, and how to limit access in Timed Access Control.

An Obscure Option to Improve Apple TV

Hidden in AirPort Utility’s Network options below DHCP Lease on 802.11ac base station models is an odd duck: a checkbox named Enable IGMP Snooping (Figure 60). Who is IGMP? Why are we snooping on him or her? Turns out, IGMP is Internet Group Management Protocol, and it’s used for multicasting, or sending data that multiple computers and devices can receive at once.

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Figure 60: IGMP Snooping doesn’t turn the base station into a spy, but can make AirPlay function more smoothly.

While this doesn’t sound like something you encounter commonly, AirPlay streaming and Google’s Chromecast use multicasting, even though there’s typically only a single destination. If you check Enable IGMP Snooping, your base station optimizes network multicast messages, which reduces unnecessary traffic, and can produce a better result with AirPlay. If you’ve been having trouble using AirPlay over a network, check this box, click Save, click Update, and after your base station boots, see if things have improved.

Dynamic Public Addresses

Some people request public addresses from their ISP to use for their LAN computers; this allows each computer to be reachable from the public Internet without any intermediary address translation. In this case, you usually want to configure each computer manually with a static public address and DHCP isn’t involved. However, some networks use only public addresses for all connected devices, while also not requiring that each device have a static address over time. In that case, you configure a base station to hand out public addresses from a defined range using DHCP.

To configure a base station to assign dynamic public addresses, follow these steps:

In AirPort Utility for Mac, select the base station, click Edit, and then click the Network button.

Choose DHCP Only from the Router Mode pop-up menu.

In the DHCP Range fields, enter values for the beginning and the ending addresses. The range you specify is limited to the same IP network that the base station uses for its Internet Connection IP address. For instance, if your base station is 218.23.1.200, your range must be within 218.23.1.1 and 218.23.1.255.

Tip: As described in a tip in Dynamic Private Addresses (a few pages earlier), in addition to using automatic DHCP assignment, you can set manual addresses on devices on the network outside that range.

Warning! If you use publicly routable addresses, your entire base station LAN is fully exposed to the Internet and your computers are susceptible to direct attacks by ne’er-do-wells. For example, someone could attempt to break your Web server by sending it a maliciously crafted request.

Reserved Addresses

Reservation allows a given device on a network to obtain the same IP address, whether public or private, each time it joins the network. This works whether or not you share the base station’s connection or distribute a range of addresses, but does require DHCP service to be turned on.

The reserved address is never assigned to another computer, and if the computer in question restarts or shuts down, the next time it powers up and its network adapter is active, it receives its reserved address.

Reserved addresses work well if you want to connect from the WAN side of a base station to computers, printers, and other devices that are connected via the LAN side.

Follow these steps to set up reserved addresses:

In AirPort Utility for Mac, select your base station and click Edit. Then, below the Network pane’s DHCP Reservations list, click the plus button.

A dialog for entering the reservation appears (Figure 61).

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Figure 61: The assistant lets you set up a reserved DHCP address by MAC address or by DHCP client ID.

Enter a description. It will later appear in the DHCP Reservations list.

Choose whether to reserve an IP address by a Wi-Fi adapter’s MAC address or by its DHCP Client ID. (DHCP Client ID is easier to set up, but it works only with OS X, and even earlier Mac systems):

If you reserved by MAC address, enter the MAC address (AirPort Utility fills in the colons as you type the two-digit hexadecimal numbers), and enter the last number in the IP range that you want to reserve. For help with locating the MAC address, skip ahead to Appendix D: What and Where Is a MAC Address?.

If you reserved by DHCP Client ID, enter the DHCP Client ID that you set up on a Mac (see sidebar below) and then edit the last number in the four-number IP address.

Click the Save button.

If you need to reserve more than one address, repeat the previous steps until you’ve set up all your reservations.

After completing all the reservations you need, click Update.

When the base station is finished restarting, the DHCP Reservations list shows the entries you made and any computers listed will have retrieved their new addresses.

Setting the DHCP Client ID

The DHCP Client ID is a text tag that you assign to a Wi-Fi or Ethernet adapter. When an adapter requests a dynamic address, it transmits the text, and then the base station uses the tag to assign a reserved IP address.

To set a DHCP Client ID on a Mac:

Open the Network system preference pane, select the adapter at the left, and then click the Advanced button.

Click the TCP/IP button.

Choose Using DHCP from the Configure IPv4 pop-up menu, and enter the DHCP Client ID in the field at the right. Figure 62 shows the DHCP Client ID set to GlennMacBook. (To avoid confusing the base station, make sure that each Mac’s DHCP Client ID is unique.)

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Figure 62: The DHCP Client ID field appears when the Configure IPv4 pop-up menu is set to Using DHCP.

Click OK.

Back in the main Network preference pane, click the Apply button.

Now you can use the DHCP Client ID in AirPort Utility for Mac.

If a Mac Still Shows Its Old Address

Open the Network system preference pane, select the adapter, and click the Advanced button. Click TCP/IP, and then click Renew DHCP Lease. The IPv4 Address field should clear for a moment, and then the correct address should appear. Click OK, and then click Apply if the Apply button is active.

Passthrough and Bridging

For networks in which the base station is connected to a larger LAN, you may already have a DHCP server running that handles address distribution. In that case, you need to turn off Connection Sharing:

In AirPort Utility for Mac, select your base station, click the Edit button, and click the Network button.

Choose Off (Bridge Mode) from the Router Mode pop-up menu. (The Network Options button dims.)

Click Update to restart the base station.

With Bridge mode, the base station simply passes through any DHCP messages or other traffic, and isn’t involved in assigning addresses.

Connect Your Devices

Once you’ve set up a Wi-Fi network and connected it to the Internet, you’ll want to configure your devices to connect to it, whether you’re working in your own home or helping customers with a public hotspot.

Read this chapter to learn how to connect in OS X (just ahead), Connect in iOS, Connect in Windows 10, Connect in Android, and Connect in Chrome OS.

Note: Just because a network is visible doesn’t mean you can connect to it. MAC address access control and other restrictions could keep you from joining. See Secure Your Network.

Connect in OS X

If a Wi-Fi network appears nearby and your Mac isn’t already connected to one (for instance, if a neighbor turns on a new network or if you open your laptop in a coffee shop), OS X will alert you (Figure 63). From that alert, you can then connect to the network.

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Figure 63: OS X alerts you to a new network.

Tip: If you aren’t prompted to join a network, you’ve disabled a setting in the Network system preference pane. See Refine Your Connection Options.

Your Mac will automatically join any network that it’s been told to remember: it will connect when you wake it up or turn it on, when you turn Wi-Fi off and back on, when a network is turned on nearby, or even when a Wi-Fi network disappears and reappears while you’re actively using the computer.

You can also join a Wi-Fi network by choosing it from the Wi-Fi menu on the system menu bar (Figure 64). A Mac regularly looks for networks, and a list of any found networks appears in this menu when the Wi-Fi adapter is on. (If it’s off, choose Wi-Fi > Turn Wi-Fi On.)

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Figure 64: Choose a network from the list or choose Join Other Network to join a closed network by entering its name.

Tip: If you don’t see a Wi-Fi menu on the system menu bar, read Finding the Wi-Fi Menu, earlier.

To join a network when the network broadcasts its name—as most do—choose the network name from the Wi-Fi menu:

Configured networks appear in the main list.

iOS personal hotspots show up at the top under the label Personal Hotspot if the Mac is new enough and the iOS device is running iOS 8.1 or later.

Ad-hoc and computer-to-computer networks appear under a Devices label.

Apple base stations yet to be configured appear under New Type of Unit Base Station

To connect to a closed (hidden) network, choose Join Other Network.

Warning! Public Wi-Fi networks won’t appear in the Devices list; if you see a public-sounding network there, it is likely a compromised computer, a bad configuration, or a hacker trying to get you to connect to a honeypot.

If you’re asked to enter a password, go ahead and do so; I talk more about picky password details just ahead, in Enter a Password. (If you chose Join Other Network, enter the network’s precise name—close doesn’t count—and choose None from the Security menu or pick the form of encryption and enter the username—if required—and password.) Click Join.

OS X animates the bars in the Wi-Fi icon, lighting them up one at a time in a back-and-forth pattern while the connection is being made.

Tip: If the bars continue don’t stop oscillating and you see this icon , the network couldn’t assign an IP address. See Wi-Fi Network Won’t Assign IP Address for a fix.

After the connection is completed, the Wi-Fi menu’s icon switches from gray to black, with the number of black waves indicating signal strength by their quantity. It switches to two overlapping chain links if you’ve connected to a personal hotspot.

Although you should now be able to access the Internet normally, if the network is an unencrypted hotspot, you may see a floating window that shows a hotspot login screen. This nice touch first appeared in Lion; it avoids you having to remember to launch a Web browser after connecting to agree to terms of service or to handle any account or fee details. This window can be dismissed by clicking Cancel. After agreeing to the hotspot’s terms or entering login details, if the window doesn’t close by itself, click Done.

Note: If you don’t see this window and can’t access the Internet form the hotspot connection, launch a Web browser and try to visit a Web site. This should cause the hotspot access page to appear.

How Apple Knows You’re at a Hotspot

Apple uses a trick to check if you’re at a hotspot. In iOS and on the Mac, whenever you connect to any Wi-Fi network, the operating system tries to perform a DNS (domain name service) lookup for the address www.apple.com and then check in with an Apple server. If the returned address isn’t correct or the connection doesn’t go through, this means the hotspot has an interception or gateway system in place that rewrites DNS or blocks connections until you have passed whatever hurdles it has set up.

Apple uses that bit of information to bring up its hotspot screen showing whatever the gateway returned instead of the Apple.com home page.

If you ever see the hotspot login screen appear and it displays Apple.com, you know there’s something very wrong with the local network! Once Apple had trouble with its DNS, which prompted the hotspot login screen to appear on everyone’s attempt to connect to a network everywhere.

Enter a Password

If encryption is active on the network, after you choose the network name, you are prompted by a dialog to enter a password (Figure 65).

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Figure 65: When you attempt to join a network that’s protected by encryption, you’re prompted for its password.

Typically, the Wi-Fi software on a Mac automatically chooses the correct encryption type, and you simply enter the password you’ve been given (or that you’ve set yourself for the network, if it’s your network) and then click Join to connect to the network.

Storing Passwords

You can store the password in the Keychain by leaving Remember This Network checked; this prevents you from having to retype it in the future.

You can run Keychain Access (found in /Applications/Utilities/) to delete entries you no longer wish to store or to retrieve passwords that you have forgotten.

Keychain passwords are secured with your OS X user password, unless you set a special Keychain password, which you can do in Keychain Access by choosing Edit > Change Password for Keychain “keychain name”.

You may have questions about which format to use when entering the password, or what to do if after entering it you cannot connect to the network. Read on for those details.

Extracting a Hex Key

In exceedingly rare cases with WPA, you may need to enter a 64-digit hexadecimal encryption key that’s hidden from view. In over a decade of using WPA, I have never had to enter such a key.

To enter this in Lion or later, hold down the Option key before you choose the network from the Wi-Fi menu. An extra large field labeled Key appears, allowing entry. (When using Join Other Network, hold down Option to select a security method.) Yes, it’s a pain to enter 64 hex digits. It’s there for full compatibility’s sake.

To find an Apple base station’s full WPA key, select your base station, click Edit, and choose Base Station > Show Passwords. The WPA Pre-shared Key appears, and you can copy it as plain text from its dialog.

Manage Network Profiles

Wi-Fi network profiles work on Macs running 10.5 Leopard and later. They let you enter and store any needed passphrase, key, or login details to access a network. You can manage Wi-Fi network profiles in the Network system preference pane.

Tip: iCloud Keychain will sync Wi-Fi network names and passwords among all your iOS and OS X devices logged in to the same iCloud account on which iCloud Keychain is enabled. But see the Warning! below.

Open the pane and select the Wi-Fi adapter; then click the Advanced button to see more options in the Wi-Fi view (Figure 66).

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Figure 66: You can add, delete, and prioritize networks with which you want to connect without re-entering details.

To manage your profiles, use the following options:

Add a profile by clicking the plus button. (If the checkbox Remember Networks This Computer Has Joined is enabled, new profiles will be created automatically as you join new networks.)

Delete a profile you no longer need by selecting it and clicking the minus button.

Warning! If you have iCloud Keychain enabled, deleting a profile deletes its entry, including its password, from all associated devices.

To change the preferred order in which the computer connects to networks if more than one is available, drag a network name to a new position in the list.

Note: If you make a mistake when creating a profile, or need to change the encryption method or password, you have to delete the profile and create a new one. Silly, really.

Manage Network Locations

OS X lets you take all your specific network settings for adapters and collect them into a location. A location is useful, because you may have different networking requirements in different places that you frequent, such as your workplace, your sister’s house, or the library. Some third-party software can use geofencing—identifying an area based on coordinates—to swap locations automatically for you.

To work with locations, open the Network system preference pane and see what’s on offer in the Location pop-up menu at the top of the pane. You can choose any location in that menu, including the default Automatic, and then configure it using the list at the left, below. This can include removing adapters, marking them as inactive, and dragging them to re-order their priority. For example, you might want a device to connect preferentially over Ethernet, when possible. All these options appear in the gear pop-up menu (Figure 67). Click Apply when you finish.

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Figure 67: The Location pop-up menu at the top of the Network preference pane lets you swap between adapter settings.

Note: If you use the gear pop-up menu to disable the Wi-Fi adapter, the system menu bar shows a unique icon: .

To set up another location, follow these steps:

From the Location pop-up menu, choose Edit Locations to see an editable list of locations.

Click the plus button, and name the new location (Figure 68). (You can also select an existing location and, from the gear pop-up menu, choose Duplicate, and then name it descriptively.)

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Figure 68: The Locations dialog lets you add, remove, duplicate, and rename network locations.

Now, with the new location chosen in the Location pop-up menu, make your desired changes to the interfaces list at the left.

Click Apply.

You can swap among locations in the Network preference pane by choosing a new location from the Location pop-up menu, and then clicking Apply; however, it’s usually more convenient to choose a new location from the Apple  > Location submenu. (This submenu appears only if you have defined more than one location.)

I use Location at my house, because of an erratic broadband connection. I have one Location set to my ISP’s name; another to Personal Hotspot via USB. It’s a quick Apple  menu choice when the network becomes unreliable.

Warning! Wi-Fi networks in the profile list described next are shared in all locations.

Refine Your Connection Options

To control some of how a Wi-Fi adapter connects to networks, select the Wi-Fi adapter in the Network system preference pane, and do any of the following:

Select Ask to Join New Networks to have the Mac alert you when it finds a network that you’ve not stored a profile for (Figure 69).

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Figure 69: If this checkbox is checked, when the Mac spots a new network, you’re asked if you want to join.

Click the Advanced button to reach additional options:

If “Remember networks this computer has joined” is checked, the Mac adds a profile for any network you join, whether a password is required or not. The box is selected by default.

The “Require administrator authorization to” checkboxes allow you to override someone’s attempt to create computer-to-computer (ad hoc) networks, switch networks, or turn Wi-Fi off.

Learn from the Wi-Fi Menu

The Mac scans for networks every few seconds and dynamically updates the list even after you open the Wi-Fi menu (Figure 70).

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Figure 70: When you first open it, the Wi-Fi menu displays the label Wi-Fi: Looking for Networks. It then lists networks that your Mac has found.

Networks appear in alphabetical order, with the network you’re connected to coming first. A lock icon appears to the right of protected networks—those using WEP, WPA, or WPA2. The menu also shows a signal strength indicator to the right of the network name.

Various labels may appear in the Wi-Fi menu. Two show up below the list of standard Wi-Fi networks and above the Join Other Network item: Devices, which shows any printers or computer-to-computer or ad hoc networks (see Ad Hoc Networking), and New AirPort Base Station, which shows any unconfigured devices on the local network available via Bonjour (Figure 71) (read Set Up a Network).

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Figure 71: A separate area in the Wi-Fi menu shows any unconfigured base stations by type.

Devices and the New AirPort Base Station appear only if an appropriate device or new base station is available.

Any iOS personal hotspots are shown above the list of base stations under their own label if you’re running Yosemite or later and the iOS device is running version 8.1 or later (Figure 72).

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Figure 72: Personal hotspots, such as the Executive Privilege network shown here, appear above other networks.

Tip: The Wi-Fi menu shows a host of extra details when you hold down Option before selecting it. See Use the Wi-Fi Menu for the full rundown.

Disconnect

Once a Mac is connected to a standard Wi-Fi network, it used to be fiendishly difficult to disconnect it. (Ad hoc networks can be disconnected with a Wi-Fi menu item.) As of Yosemite, there are now many options. While still in range, you may:

Hold down the Option key and open the Wi-Fi menu. The menu item Disconnect from Current Network Name appears. This menu item also appears without the Option key if the Mac is connected to a Personal Hotspot. Choose it, and the Mac is disconnected from the network and will not re-join it unless you select it again or the device leaves the range of the network and returns.

Choose Turn Wi-Fi Off from the Wi-Fi menu. This disables the device’s network connection entirely.

Connect to a different network.

Remove the network profile:

In the Network system preference pane, select the Wi-Fi adapter in the list at left and then click the Advanced button.

In the Wi-Fi view, select the network in the Preferred Networks list and click the minus button.

Click OK, and then click Apply.

You may additionally need to turn the Wi-Fi adapter off and on from the Wi-Fi menu to have it drop the current connection.

Connect in iOS

iOS provides a simple way to join any Wi-Fi network with a few taps. If the Ask to Join Networks option is on in Settings > Wi-Fi, then whenever you’re in range of any open Wi-Fi network and not already connected to one, iOS pops up a dialog asking if you want to join. Tap the network you want, and enter a password if one’s requested.

Note: The figures and details here are for iOS 9, but most of this topic applies to iOS 7 and 8, and even works with earlier versions.

You can also join a network by tapping its name in a list:

In the Settings app, tap Wi-Fi to open the Wi-Fi view (Figure 73).

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Figure 73: The Wi-Fi view lets you tap a network to join.

Select the network from the Choose a Network list by tapping it. (If the network you’re trying to find doesn’t appear, tap Other—you may have to slide down to find Other.)

Enter a password if prompted.

You’re now connected. Tap the blue info icon next to the connected network for TCP/IP details, such as the assigned IP address.

A Chain-link Icon Indicates a Personal Hotspot

Apple uses a chain-link icon to indicate when a Wi-Fi network has been created using the Personal Hotspot feature in iOS, either on an iPhone 4 or later, an iPad mini, or a third-generation iPad or later. Personal Hotspot lets the iOS device act like a cellular router for other devices.

With an iOS 8.1 or later device with Personal Hotspot capability and another iOS 8.1 or later device trying to connect to it, the Personal Hotspot appears in the Wi-Fi list under its own label, while also showing the chain-link icon.

To disconnect while in range of the network, do either of the following:

Tap Settings > Wi-Fi and turn off the Wi-Fi switch to disable the Wi-Fi adapter. While it remains off, you’re disconnected.

Tap Settings > Wi-Fi, tap the blue info icon by the currently connected network, and tap Forget This Network. iOS immediately disconnects you, and you will remain disconnected.

Wi-Fi Assist Boosts Wonky WLAN

In iOS 9, Apple added Wi-Fi Assist, which is enable by default and allows an iOS device to automatically tap a cellular data connection when a Wi-Fi network has inconsistent or no Internet access. It works on all iOS 9-capable devices except the iPhone 4s, and the Wi-Fi + Cellular iPad 2, 3rd-generation iPad, and 1st-generation iPad mini.

Wi-Fi Assist is seamless and continues to try to use Wi-Fi—but only if you’re in a home cellular area. Without this feature, the only way you could use the Internet without long pauses and drop-outs would be to turn off the Wi-Fi switch to disable Wi-Fi and force the use of cellular. The cellular indicator appears in the status bar whenever it swaps over.

Apple tries to make sure you don’t suck down cellular data when this mode is enabled, so it allows only foreground usage: it won’t continue downloads in the background, among other background tasks. It also doesn’t allow streaming audio or video, nor will it download email attachments.

Despite Apple’s precautions, I suggest extreme care with this feature if you don’t have unlimited cellular data or a high monthly limit. You can try it out and monitor your usage so you don’t wind up with a whopping overage charge or hitting a cap and then being throttled, depending on your plan.

The switch for turning Wi-Fi Assist on or off is found in Settings > Cellular at the very bottom of the view, so if you have a lot of apps, you have swipe way, way, way down to reach it.

Connect in Windows 10

To connect to a network in Windows 10 or later, follow these steps:

Click the Wi-Fi menu in the System Tray.

A Networks pane appears, showing a Wi-Fi switch and any available Wi-Fi networks (Figure 74). (If you don’t see any Wi-Fi networks listed, make sure the Wi-Fi switch is turned on.)

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Figure 74: The Networks pane shows which network is connected, if any (Portage Airbasestation in this case), as well as the names of any other available networks. You can also disable Wi-Fi (by clicking Available at the lower left) or all radios (by clicking Airplane mode).

Click the network to which you want to connect, and optionally enable the checkbox to Connect Automatically. Then click the Connect button.

If a password is requested, enter it and click Next (Figure 75).

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Figure 75: Enter the network’s security key, and click Next.

If the connection is successful, you’ll see a Connected label appear beneath the network’s name in the Networks pane.

Note: Microsoft added the Share Network with My Contacts option in Windows 10, as shown in the figure above. For password-protected networks, you can automatically provide access to Outlook.com contacts, Skype buddies, and Facebook friends (or any one or two of those three categories). Unless you’ve been given permission to share a network, don’t check that box.

Connect in Android

It’s just a few steps to connect to a Wi-Fi network in Android. The steps are more or less the same for most recent releases; these were prepared with Android 5.1:

From the home screen, tap Settings.

Tap Wi-Fi.

A list of networks should appear (Figure 76).

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Figure 76: Android shows the list of available networks.

Tap the network you wish to join.

If it’s password protected, you should be prompted to enter the security key (Figure 77). Tap it in, and tap Connect.

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Figure 77: Enter the password and click Connect. You can tap Show Password to keep characters visible after you type them.

Connect in Chrome OS

Google’s Chrome OS runs the many inexpensive, powerful, cloud-connected notebook computers known collectively as Chromebooks, though they are made by many different hardware manufacturers.

You can easily connect from Chrome OS to an Apple base station, just as to any other Wi-Fi router, by following these steps, which are quite similar to Android, but not identical:

At the lower right of the screen, click the Status bar at the lower right of the screen. A panel appears with the current state of the Chromebook (Figure 78).

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Figure 78: The status bar show network status, including this x’d out icon if there’s no currently connected network.

A panel appears, showing the current state of the Chromebook (Figure 79).

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Figure 79: The Chrome OS status area includes networking.

Click the network area, which may show a Wi-Fi network name or say No Network.

A list of available networks appears. Click the network you want to join (Figure 80).

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Figure 80: Chrome OS displays available networks.

If the network is password protected, you’re prompted to enter that password (Figure 81). (Click the “eyeball” icon to see the password as you type.) Click Connect.

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Figure 81: Enter the network password when prompted.

If the password was entered correctly and the network is working properly, the Chromebook connects to the network. You can click the status bar to confirm the connection (Figure 82).

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Figure 82: Now, a connected message appears in the status panel.

AirPort Express Extras

The AirPort Express, for its modest size and price, includes several features found in neither a Time Capsule nor an AirPort Extreme, mostly around music. The Express also hides a nifty connection option for extending a network.

Stream Audio with AirPlay

AirPlay is a method of streaming media from a computer or iOS device to an external output device, such as an AirPlay-compatible speaker or an Apple TV, or—most interestingly for our purposes—an AirPort Express.

In the case of the AirPort Express, only audio can be streamed. The Express sends the stream through its audio output port (Figure 83) to stereo speakers. You control the settings in AirPort Utility, and then play the audio from an iOS device or from a Mac.

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Figure 83: You can stream music from a computer on the network through AirPort Express to a stereo or powered speakers.

Note: AirPlay audio streaming works from an iPhone 4 or newer, a 4th-generation iPod touch or newer, and any iPad or iPad mini. It also works from any Mac running 10.8 Mountain Lion or later; older Mac systems can stream audio to the AirPort Express, but only from iTunes 10.2 or later.

Note: All but the first generation of the Apple TV can receive AirPlay mirroring from AirPlay-compatible iOS devices and from most moderns Macs. Read Take Control of Apple TV for more information.

Set Up AirPlay

To set up AirPlay, open AirPort Utility and edit your AirPort Express’s configuration. Click or tap the AirPlay button to see the AirPlay view (the Mac version is shown in Figure 84).

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Figure 84: You can set a few AirPlay options.

Ensure that the Enable AirPlay checkbox is selected, and name your AirPlay speakers. The name appears in the Mac’s remote speaker list and in the AirPlay list in iOS. You can set a password to limit use of this speaker set to people who have the password. Click Update to apply changes.

Play Any Audio from OS X

To stream audio from your Mac to an AirPlay device, go to System Preferences > Sound > Output, and select an AirPlay option from the list of output choices—look for an AirPlay designation in the Type column. If a password is set, you are prompted to enter it. The volume on your computer controls the remote volume.

Tip: You can switch your Mac’s audio output to a different device (including an AirPort Express) by pressing Option while you open the Sound menu on the menu bar and then choosing the desired device.

Play Audio from iTunes

In iTunes 12, the AirPlay icon is near the top left of the window, beside the volume slider. Click this icon, and you can choose a device to use for audio or video output (Figure 85). An icon next to each device name shows whether the device can play video or just audio, and a lock on an icon indicates that a password is required.

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Figure 85: The AirPlay popover in iTunes 12 shows all available devices on the network.

Click Multiple (as shown above) to activate a list of all available AirPlay devices. Select the devices you wish to use. You can use the Master Volume slider at the top to set the overall output volume, and balance each device with its associated with slider.

Use the Remote App to Control Music

Apple’s free Remote app runs on the iPad, iPhone, and iPod touch. It can connect over a local network to iTunes for Mac or Windows. If iTunes is streaming audio to an AirPort Express, then Remote and its volume control can handle whatever’s coming out of your AirPort Express audio port.

Here are a few more things you might like to know about AirPlay:

No speakers: If you select an AirPort Express with no speakers connected, iTunes will let you know (Figure 86). The AirPort senses whether there’s a plug in place.

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Figure 86: You can’t play music if there’s nothing plugged in!

Two people: If you try to play music through an AirPort Express or other device that someone else is actively playing music through, iTunes notifies you when you press Play. If that person clicks Pause, iTunes releases that person’s control, and within 2–3 seconds, you can start playing music through that device.

Password protection: You can password-protect AirPort Express music streaming (as noted a few pages earlier). For instance, if you live in a dorm, you might want to prevent pranksters from blasting through your speakers.

Tip: A few remote speaker models can control iTunes remotely when connected via an AirPort Express or as part of a Wi-Fi network. To control this behavior, check or uncheck Allow iTunes Audio Control from Remote Speakers in the iTunes Devices preference pane.

Play Audio in iOS

You can play audio from any app to an AirPlay device, including an AirPort Express:

From any app that offers audio output, tap the AirPlay button and choose the AirPort Express as the destination.

Swipe up from the bottom of the screen to bring up the Control Center and then tap the AirPlay button to select the AirPort Express.

If an AirPlay device doesn’t appear when you think it should, try switching into Airplane Mode on the iOS device briefly. If that doesn’t help, try restarting the AirPlay device.

As in OS X, if an AirPlay destination is already in use by someone else, you’re alerted (Figure 87).

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Figure 87: Only one source can control a set of “remote speakers,” whether an Apple TV, powered speakers, or an AirPort Express.

Share with Airfoil

Rogue Amoeba’s Airfoil software ($25, downloadable demo version) for OS X and Windows is a tour de force for streaming audio and for syncing audio with video playing on another device among different computers, handhelds, and devices.

It has several advantages over OS X’s AirPlay:

You can send audio to other Macs, not just to an Apple TV, AirPlay speakers, and an AirPort Express (you can send to those as well).

You can send audio to multiple output devices at once.

Airfoil can send audio to 10.9 Mavericks and later, iOS 4.0 and later, Android, and Windows, so it supports a greater variety of devices.

Note: Airfoil is available for Windows, but there’s also a free, separate receiver app for Mac, Android, and Windows called Airfoil Speakers and an iOS app dubbed Airfoil Speakers Touch. These programs may be used as the “receiver” to enable streaming to those devices from Airfoil.

iTunes by itself can stream music over AirPlay only to an AirPort Express, an AirPlay-enabled speaker or other audio device, or an Apple TV. iTunes can also stream video to an Apple TV. Airfoil extends your streaming options tremendously; you can:

Stream audio from iTunes on Mac or Windows to an iOS device using the Airfoil Speakers Touch app as a receiver.

Stream audio from any program on a Mac or in Windows to an AirPlay device (like an AirPort Express), a computer, an iOS device, or an Android device. (At times, you may want to stream just a single app’s audio, but not all the beeps and pings that your system audio may include.)

Airfoil Speakers on a Mac and Airfoil Speakers Touch (version 3 or later) can appear as an AirPlay destination to an iOS device with no special software installed on the iOS device.

The advantage here is that you’re not limited to iTunes or an iOS device, nor to playing audio only via AirPlay-enabled hardware.

To use Airfoil with an AirPort Express, follow these steps:

Launch Airfoil.

The main screen shows which output targets are available on the local network (Figure 88).

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Figure 88: Airfoil showing the audio outputs available on my local network. From top to bottom, that’s the computer on which Airfoil is running, an AirPort Express (locked with a password), an Apple TV, and my iPhone running Airfoil Speakers Touch.

Choose an audio source from the pop-up menu at the top of the Airfoil screen.

Click the speaker icon to the right of the AirPort Express; in this example, it’s Guest Room Speakers.

If there’s a password, you’re prompted. Enter it, just as with iTunes.

Now you’re connected. Any audio playing from the source you chose in Step 2 is now pumping out of the AirPort Express.

Tip: Airfoil can play many kinds of Web video on a remote system, while playing the audio locally or elsewhere and keeping it in sync.

Connect to Any Base Station

The AirPort Express has a special, lightly documented mode that allows it to connect wirelessly to any Wi-Fi network, not just other Apple base stations, and share the connection via Ethernet. This mode, called ProxySTA by Apple but not mentioned by that name in Apple’s documentation, is handy for using the Express in circumstances where you can’t control how the network works.

Note: The term ProxySTA refers to a base station acting as a proxy, a kind of intermediary, between your computers and a Wi-Fi network; and acting as a station, the technical 802.11 term (abbreviated STA) for an adapter. An adapter connects to what we and Apple call a base station, but which is known more precisely as an access point (AP).

With ProxySTA, AirPlay streaming and printer sharing work the same as they do when you use them with Wireless Distribution System (WDS) or connect the base station via Ethernet to the rest of a network.

With ProxySTA, Ethernet clients—computers connected directly or multiple computers connected via an Ethernet switch—must obtain a DHCP address through a passthrough connection on the network that the Express has joined.

To use ProxySTA mode, follow these steps:

On your Mac, launch AirPort Utility, select the Express, and click Edit.

Click the Wireless button.

From the Network Mode pop-up menu, choose Join a Wireless Network (Figure 89).

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Figure 89: Choose a network and enter its password, if any.

Choose the network from the Wireless Network Name pop-up menu (or for a closed network, type the network name), choose the appropriate security method, enter the network’s password, and re-enter it for verification. (AirPort Utility fills in the password if it’s a network you’ve previously joined and chosen to remember on this computer.)

Click Update.

Now your Express is connected to the Wi-Fi network, and any computer connected to its Ethernet port, or via an Ethernet switch plugged in to its Ethernet port, can access that Wi-Fi network, and, presumably, the Internet via that Wi-Fi network.

Connect Multiple Base Stations

Wi-Fi was once described as reaching “only” about 150 feet, which is a rough estimate of the radius of older 802.11b and g devices; with 802.11n and ac, the distance is sometimes cited as longer, or just as “farther,” because it’s impossible to characterize with any precision how Wi-Fi signals will pass through any arbitrary house, office, café, airport, or store. Also, range measured as a linear dimension misstates the problem of volume, the three-dimensional space to fill.

But you can extend the covered volume by adding more base stations with overlapping signals. As a Wi-Fi adapter in a device moves across overlapping regions, it can automatically switch base stations while maintaining a network connection.

Know the Basics

When you extend a network, the additional base stations tend to be dumb; that is, they don’t assign addresses or handle other features you think of as belonging to a base station. Rather, one base station remains smart, offering DHCP and NAT (if needed), among other network choices. The rest pass through traffic from that main unit. Dumb base stations are often called access points to distinguish them from gateways.

Because dumb base stations (access points) just pass traffic through, an adapter retains the same IP address as it switches from one base station to another, thus maintaining its connection in most cases.

There are two mix-and-match methods of extending your network:

Add base stations via Ethernet. Ethernet requires wires, of course, but has a huge speed benefit over wireless extensions.

Add base stations wirelessly via Wireless Distribution System (WDS). This method avoids new wires, but can have severe speed limitations in comparison to Ethernet.

I write “mix and match” because you can use any combination of Ethernet and WDS to build a network. Let’s start with the simpler case, which is to Add Access Points via Ethernet. After that, there’s a sidebar about Extending with HomePlug, in case you want to use your home’s electrical system in place of Ethernet. And, finally, I talk about how to Bridge Wirelessly.

Create or Extend a Network

When you work in AirPort Utility to build a network of two or more base stations, connecting them with Ethernet, Wi-Fi, or a hybrid, you will need to choose an option from a pop-up menu in the Wireless View. Those options may confuse you, so let’s look at them first. For each base station, in the Wireless view’s Network Mode pop-up menu, you can choose either of two options:

Create a Wireless Network is for either a main base station in a wirelessly connected network (or pod of access points), or each base station connected via Ethernet.

Extend a Wireless Network might seem like the right option for adding a base station via Ethernet, but it’s not. Extend a Wireless Network refers only to extending wirelessly: when you connect two or more base stations with Wi-Fi, the additional base station(s) that have only a wireless connection to the network use this Extend option.

What about ProxySTA?

The ProxySTA mode of extending an existing Wi-Fi network with an Express is another method, but it has its limits: it works only with an AirPort Express, and it allows only the extension of the network via the LAN Ethernet port on the Express. In contrast, linking base stations with Ethernet and WDS creates a larger and full-featured LAN with both Wi-Fi and Ethernet connectivity.

See Connect to Any Base Station, a few pages earlier, for details on ProxySTA.

Spectrum Differences

Simultaneous dual-band base stations complicate planning a network because the two spectrum bands have different coverage areas. In Figure 90 you can see a highly simplified look at the how the 5 GHz and 2.4 GHz ranges compare.

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Figure 90: You can overlap just one band and still gain seamless coverage.

In the figure, the 2.4 GHz networks overlap in coverage, while the 5 GHz networks do not. This should work fine because all of your devices can either use only the 2.4 GHz band or can roam from 2.4 to 5 GHz and back again—as long as all the base stations and bands share the same network name. (I explain how to set this up next).

On each simultaneous dual-band base station, if you name the 5 GHz network with a different name than the 2.4 GHz network, roaming will fail in an area where neither 5 GHz network has coverage.

Add Access Points via Ethernet

The advantage of Ethernet is that you get the best possible speed between Wi-Fi clients connected via base stations to other computers, and among Ethernet-connected computers on the network. Using Ethernet lets you set each base station’s 2.4 GHz and 5 GHz channel differently, allowing separate spectrum for each base station.

When you add access points that are intended to be part of the same Wi-Fi network, they must each have the same network name, known as an SSID (service set identifier). This enables computers to move around without changing their network settings, because their Wi-Fi cards automatically and seamlessly switch from one access point to another as needed to maintain a constant connection. If you have encryption enabled, each access point must be set up with the same options and keys.

When adding access points to create a network that allows roaming, you need a network backbone that connects all the access points. Typically, you use Ethernet cabling to connect the access points (Figure 91). However, you can also use wireless connections or electrical connections to form that network backbone, as I describe ahead in Bridge Wirelessly and Extending with HomePlug.

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Figure 91: A common Ethernet backbone connects one base station in the living room, another upstairs, and a third in the basement.

Set Up a Main Wired Base Station

Your main base station should be plugged into your broadband connection and configured to share addresses as discussed in New Network, Single Base Station.

You have two options for proceeding:

Let the base station automatically choose the channel it analyzes as best, based on a lack of interference from other networks or signals. It’s worthwhile to try this because it requires the least work.

Manually assign the channel, taking care to avoid overlapping with other base stations you’re setting up and other nearby networks.

In the United States, if you’re not getting the range that you want—especially in the 5 GHz band—follow the steps in Pick Compatibility and Set a Channel. As discussed in Channels, for the highest signal strength, you want to choose (in the United States) among channels 1, 6, and 11 in the 2.4 GHz band for overlapping base stations, and one of the upper four channels for 5 GHz. This is true for both 802.11n and 802.11ac, which always use a 20 MHz (normal width channel) as the starting point for how they expand into wider channels. (The lower four 5 GHz channels broadcast at 1/20th the strength of the highest-numbered channels.)

Set Up Additional Wired Base Stations

AirPort Utility automatically configures base stations as discussed in Extend a Network via Ethernet or Wi-Fi. However, if you have an existing base station that you want to reset to use as a wired extension of a network, you can follow these steps:

(You can alternatively reset a base station to its factory defaults and use AirPort Utility to add it to a network. See How to Return to the Factory Defaults.)

On your Mac, launch AirPort Utility, select the additional base station that you want to configure, and click Edit.

In the Internet view, choose DHCP from the Connect Using pop-up menu.

In the Wireless view, select Create a Wireless Network from the Network Mode pop-up menu.

Enter the same wireless network name as the main base station, and choose the same Wi-Fi security option and enter the same passwords.

In the Network view, choose Off (Bridge Mode) from the Router Mode pop-up menu.

In the Wireless view again, click the Wireless Options button. As with the main base station, either leave channel selection set to Automatic or choose a fixed channel. To choose a channel, see Pick Compatibility and Set a Channel and choose in this manner:

In the 2.4 GHz band (802.11b, g, or n) in the United States, any three base stations can uniquely use channels 1, 6, and 11 with the least interference wherever signals overlap. If you set your main to 1, set an additional one to 6, for instance. Click Save.

In the 5 GHz band (802.11a, n, or ac) in the United States, none of the channels overlap. But in 802.11n’s “wide” channel mode, a base station uses the equivalent of channels 36 and 40 at the same time. Choosing channels eight numbers apart for base stations that have overlapping signals produces the best results; those would be 36, 44, 149, and 157. Pick 149 and 157 for the strongest signal. With 802.11ac, pick either 36 or 149; 149 will provide the strongest signal. Click Save.

Tip: As noted earlier in this chapter, you can set up overlapping 2.4 GHz networks where 5 GHz network coverage doesn’t extend. In that case, you don’t have to worry nearly as much about reusing the same channels in 5 GHz.

Click Update to restart your base station with the new settings.

Now you can plug the additional access point into your main base station via Ethernet, connecting the cable from the WAN port on the additional access point either to a LAN port or to an Ethernet switch connected to a LAN port on the main base station.

Extending with HomePlug

For several years, electronics makers have been creating ever-faster powerline networking systems in which data is encoded as a component of the alternating current power that flows through homes and offices. The current fastest flavor is 1,200 Mbps—that’s a raw rate, not the actual throughput, however. A set of two adapters costs about $80.

With powerline networking, you typically use Ethernet wall plugs. Connect a computer or Ethernet switch to one of these bridges, and then plug the bridge into the wall. All similar bridges plugged into other sockets extend the network by communicating with all the other bridges. Powerline network adapters must be plugged into wall sockets, not power strips, and they’re often quite big wall warts.

To extend a wireless network, place your access points in appropriate locations, configure them as described above for an Ethernet network extension, and then plug them into powerline Ethernet bridges.

For more buying advice, consult the Wirecutter’s exhaustive guide, which I helped to edit.

Bridge Wirelessly

Wireless Distribution Service (WDS) is a neat way to extend an AirPort network without running wires between locations. As I noted earlier, if you want to extend a network by adding access points, you might connect them via Ethernet—which means more wires. Instead, WDS can connect an access point to other access points as easily as wireless clients connect to an access point.

Mixing Ethernet-backed and WDS Networks

You can mix and match WDS with Ethernet-extended networks, too. Each cluster of WDS machines can work together, and then the “main” base station in that group—see below—can hook into a larger network via Ethernet as an additional base station.

You can also set a main base station to be a WDS base station and to handle serving DHCP to computers over Ethernet, which allows it to be the root of both kinds of networks without additional configuration.

How It Works

WDS works much like plugging an Ethernet hub into an Ethernet switch. An Ethernet hub interconnects devices to each other as a single segment, just like wireless clients connecting to a wireless base station. An Ethernet switch, by contrast, isolates each port as a separate segment. A computer connected to a hub connected to a switch’s port can reach computers on other ports’ hubs because the switch has information about which computers (by MAC address) are on other segments; this info allows the switch to transfer data across segments.

Likewise, WDS allows access points to exchange information about where computers and other devices are located on a physical network. One access point can then route data to another or to a series of other access points to reach the destination computer (Figure 92).

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Figure 92: Wirelessly connected base station need to be placed only within Wi-Fi range to spread service around a house or office.

All base stations must be in range of one another for WDS to work in either mode. With the simultaneous dual-band base stations, dynamic WDS tries to connect over both bands; if just one band can be reached on another device, the base station will still connect.

If you’re not sure if one base station will be able to see another, use a laptop to test reception for a given location with an active base station. Base stations have far better antennas than laptops do, so even a marginally functional laptop Wi-Fi link suggests that a WDS connection will work.

Distribute Wirelessly

AirPort Utility automatically configures new or reset base stations to join existing networks, and that’s true for both Ethernet and Wi-Fi. You can follow the steps in Extend a Network via Ethernet or Wi-Fi for an unconfigured base station. However, you can reset a configured base station as a main base station or an extension. The following instructions provide the details.

Configure the main base station:

In AirPort Utility for Mac, select your main base station and click Edit; then in the top of the window, click Wireless.

In the Wireless view, from the Network Mode pop-up menu, choose Create a Wireless Network (Figure 93).

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Figure 93: Set up a main base station by letting it create a network and allow its extension.

Set other base station options, such as wireless security.

Click Update to restart the base station with those settings.

Configure additional base stations:

In AirPort Utility for Mac, select the appropriate base station and click Edit; then in the top of the window, click Wireless.

In the Wireless view, choose Extend a Wireless Network from the Network Mode pop-up menu (Figure 94).

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Figure 94: Other base stations connect to the main by its network name, and can optionally allow Wi-Fi connections from clients.

Choose the Wireless Network Name from the pop-up menu, or enter a name if the network is closed (not broadcasting its name).

Set your Wireless Security choice and Wireless Password to be identical with your main base station.

Click Update.

You should be prompted after the base station restarts for the base station password of the main unit. (If the password is the same for the main and additional base station, you may not be prompted.)

Note: It may take a moment after restarting for the base stations to find each other because each base station has to scan for other base stations. This is true even if you set the main base station to fixed 2.4 and 5 GHz channels.

Reach Your Network Remotely

When you share an Internet connection among one or more computers on a local network using private addresses, you give up having an easy way to connect from the outside world to a service, like a Web server or fileserver, that’s located on one of those local computers.

Public IP addresses allow anyone on the Internet to connect directly to a computer, barring any firewalls or other blocks in place, but private IP addresses are specifically non-routable without a bit of extra work.

You can also access your base station remotely for file sharing and configuration using an iCloud account and Back to My Mac.

Know Your Options

You can choose from several different methods of reaching your network from the outside world:

Basic port mapping and reserved addressing: While earlier Apple base stations offered port mapping, a way to connect a public port on a routable address on the base station with a private port on a locally connected computer, 802.11n and ac base stations also let you assign addresses to local computers on a persistent basis—these reserved addresses don’t change over time. When the base station is restarted, or when the computer is restarted, the same address is assigned to the computer once again.

This reservation system makes the mapping system work consistently with less effort. I cover how to map ports for remote access just ahead after this list.

Punch through from certain programs: A protocol from Apple called NAT-PMP (NAT plus Port Mapping Protocol) helps with port mapping without requiring you to do any special configuration on a computer or a base station. This option works only when the software you’re using is aware of NAT-PMP and can talk to the base station with this protocol, and when you have a publicly reachable IP address assigned to your base station. You can find out more in Punch Through with NAT-PMP.

Use one computer as your default host: There’s a coarser way to make NAT work, too, allowing a single computer behind the NAT gateway to act as though it’s directly connected to the Internet. This option is appropriate in limited cases where you want a machine to be reachable from the Internet on any of its ports without getting publicly reachable IP addresses from your ISP for computers on your network. I describe this default host option in Set a Default Host for Full Access.

Configure and monitor a base station and mount attached disks via Back to My Mac: If you have an iCloud account, you can access your base station remotely via AirPort Utility for Mac in 10.7 Lion or later. Once you’ve accessed it, you can reconfigure it or mount any internal (Time Capsule) or USB-attached disks. I provide directions in Access a Base Station via iCloud.

Map Ports for Remote Access

Port mapping relies on network address translation (NAT). NAT acts as a gateway between a WAN IP address for a router reachable from a larger LAN or the public Internet, and the private addresses hidden behind NAT on the base station’s LAN.

NAT Maps Private to Public Connections

When a computer within the LAN wants to connect to the Internet, the NAT software creates an association between that computer’s outgoing connection and a public port on the WAN IP address of the base station. (I talk more about Ports in the sidebar slightly ahead.)

When, for instance, a LAN-connected computer wants to retrieve a Web page, that computer might send a request from its IP address (192.168.1.100) using port 5509. (Ports for outbound connections are arbitrarily numbered above 1024.) The NAT server receives that connection and creates a request over the Internet using the WAN IP address and typically a different port. So the NAT gateway’s request might originate from a public address such as 36.44.0.6 with a port of 12087.

The Web server receiving the request doesn’t know about the original computer behind the NAT. Rather, the Web server responds by sending HTML for the requested Web page to port 12087 on IP 36.44.0.6. The NAT server retains a list of associations between public and private ports and addresses, and hands that Web connection over to the machine that originally requested it. This process is ugly, but it works reliably, almost all the time.

Port Mapping Maps Public to Private Connections

With port mapping, you create a persistent connection that allows computers outside the LAN to connect to computers inside the LAN. This port mapping lets you expose very limited services in a way that you fully control.

When you map a port, you make the gateway connect one of its Internet-accessible ports to the same (or a different) port on a computer on the otherwise-private inside network.

Warning! Anything you do to punch through ports or computers from the private network to the outside world reduces your security. Be careful about what you leave open. You may want to provide better security on computers that you expose in this fashion by installing active firewall and intrusion-monitoring software.

Ports

Every kind of network server you might run, including a personal Web server and your side of a multi-player online game, uses a port to communicate with the rest of the machine, network, or world. A port number in Internet networking can be compared to an apartment number in a typical postal mail addressing system: a computer has an IP address just like an apartment building has a street address, and each kind of service used by a computer has a port number, just like each apartment has its own number within the building.

With ports, it’s as if every apartment building had the manager in unit 1, the mailroom in unit 25, a lounge in unit 80, and so forth. Ports are consistent for the same services on whatever machines those services are running on.

Taking it one step further, if you have a static IP addresses, that’s like having a street-front address. In contrast, NAT-provided private addresses are like buildings within a gated compound, where nobody on the outside knows the building numbers on the inside.

If you were inside the compound, you might carry a letter to be mailed to the outside world to the compound’s mailroom, and the mail carrier would pick up your letter from there. Return mail, addressed to a mailbox number in the mailroom, is delivered only to that outer mailroom, where you can receive it without leaving the compound.

Once you’ve created a mapping, the gateway listens for traffic on the specific port on its public, WAN interface. When traffic arrives and a connection needs to be opened, the gateway reroutes the traffic from that public interface port to the appropriate private address on its LAN interface, whether that’s a Wi-Fi LAN or a wired LAN (Figure 95). In the figure, I show the example of operating a Web server and playing Half Life behind a NAT gateway.

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Figure 95: A laptop user is playing Team Fortress 2 over the Internet; another computer on the network is running a Web server. When a user in Kuala Lumpur requests a Web page, the gateway maps the incoming request on port 80, the standard port for Web servers, from its public address to the Web server’s private address. Likewise, when traffic needs to run over port 27015, the standard port for Team Fortress 2, the gateway connects traffic from a player at Indiana University with our network’s laptop user.

Using port mapping reliably has two parts: set a persistent private (“reserved”) IP address for a computer on the LAN, and then set a persistent port mapping between a port on the base station and a port on the LAN computer. In the topics ahead, I explain how to complete both of these tasks.

Set a Reserved Address

For each computer with which you want to use port mapping, you should create a DHCP reservation, which I described in Reserved Addresses, earlier. As you work, I suggest that you create a text file or other list that includes the name of each computer (described by its owner or its unique name) along with the corresponding reserved addresses. Once you’ve reserved addresses, you can set up effective port mapping.

Note: Port mapping ties a public port to a specific private IP address, so if you don’t use a DHCP reservation, you can’t easily keep port mapping working without constantly making changes to the base station configuration and restarting—which changes the IP addresses assigned dynamically!

To use port mapping, you need to know which ports to map! This can be trivial. You could map port 80 on the public side to port 80 on a given computer on the private LAN, and establish a Web server connection, for instance. For games, streaming media, and other purposes, you might need to set up a bunch of ports.

Warning! Port mapping works only on a base station that’s distributing addresses. One that’s set to bridging can’t (and doesn’t need to) handle port mapping. Instead, connect to the base station that’s feeding out addresses for the network.

Set Base-Station-to-Computer Port Mapping for a Web Server

With a Web server running on a computer on the network, we need to set up the base station to pass traffic to the newly configured port:

Launch AirPort Utility for Mac, select your base station, and click Edit.

Click the Network button.

Below the Port Settings list, click the plus button to bring up a port-mapping dialog (Figure 96).

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Figure 96: After you choose Personal Web Sharing from the Description pop-up menu, the utility fills in the correct ports.

From the Description pop-up menu, choose Personal Web Sharing (really, this means any kind of Web server). To a provide a more descriptive name, click in the Description field and type a name. (For a more advanced network setup, described below, enter all the necessary ports in this step.)

In the Private IP Address field, enter the reserved IP address. (You can edit only the last number of the IP address, as the first three numbers are set in DHCP configuration.)

Click Save.

Click Update to restart your base station with this setting.

After restarting the base station, you should attempt to connect from outside your network to the Web server you enabled, or have a friend or colleague try the connection. If the connection doesn’t work, make sure the firewall on the computer running the server is configured correctly.

One per Port

Here’s the tricky part. If you want to run Web servers on different computers on your private LAN, you can’t simply map public TCP port 80 to several computers. It won’t fly. Instead, you can use different public ports; however, then visitors who type in a domain name as the Web address can’t reach your alternative-port servers. You should use alternative-port servers only for special purposes or as servers available only by clicking a link.

All Web browsers can specify a Web server not just by domain name, but also by port, in the form http://serveraddress.com:0, such as http://tidbits.com:8001.

Say you have two private Web servers, both receiving connections on port 80. With port mapping, you would set one server’s public port to port 80 and the other to something like 8000 (a typical alternative Web server port). In port mapping, you would map port 80 to one private IP address’s port 80 and port 8000 to the other Web server’s private IP address at port 80. This avoids you having to make any changes on the Web server, and it renders the sites completely reachable.

Map Other Ports

We won’t all run only Web servers on our private networks, however, so let’s look at the options in the port-mapping dialog more closely (Figure 96, slightly earlier):

Firewall Entry Type: IPv4 Port Mapping is currently the only option and is dimmed.

Description: The pop-up menu part of this field contains the names of many common services, like FTP Access for file transfer and Apple Remote Desktop. Choosing an item from the pop-up menu fills the port fields with the correct values for that service.

If what you need isn’t in that menu, you have to look further. For games and other more complex services, read the documentation, which typically describes the necessary port-mapping settings. You can also consult the Special Application Port List, published by Practically Networked.

If you like, you can click in the field to edit the preset name.

Public and Private UDP and TCP Ports: Public and private refer to the exposed ports (the public ones) and the ports on the local computer (the private ones). UDP and TCP are two different kinds of packets that can be carried over an IP network. UDP (User Datagram Protocol) is often used for streaming media, while TCP (Transmission Control Protocol) handles Web and other kinds of connections. Any service you might want to use could have a combination of UDP and TCP ports:

Each port field can handle a single number or a range as two numbers separated by a hyphen. You can also have multiple numbers or ranges separated by commas. For instance 407, 1216-1300, 6000-7000 would be a legitimate entry.

The ports must correspond in quantity from field to field. If you enter 407, 1000-1003 in the Public TCP Ports field, you must enter at least five (407, 1000, 1001, 1002, and 1003 comprising five) ports that correspond in the same order in the Private TCP Ports field.

Punch Through with NAT-PMP

Apple has a protocol that helps with port mapping without requiring special configuration on a computer or a base station: NAT-PMP (NAT plus Port Mapping Protocol). NAT lets properly enabled programs on a computer on the LAN part of a base station’s network ask the base station for the base station’s public address. This new service can then be available remotely via Bonjour or through the WAN IP address.

To enable this feature, select your base station in AirPort Utility for Mac, click Edit, click Network at the top of the window, click the Network Options button, and select the box labeled Enable NAT Port Mapping Protocol (it’s already checked and available on new base stations or those reverted to factory settings). Click Save, and then click Update.

The downside to NAT-PMP is that each program must have built-in support to work with the protocol. With regular port mapping, software can be entirely unaware that it’s not exposed to the Internet. There’s not widespread use of NAT-PMP, because it’s not found in routers outside Apple’s.

Note: NAT-PMP is a subset of features found in the more widely supported UPnP (Universal Plug and Play), which appears in most consumer Wi-Fi gateways as an option.

Set a Default Host for Full Access

The alternative to creating reserved addresses and port mapping for each service on each computer you want to expose from your private network is to appoint a single computer as your public machine. This exposed machine could serve any kind of service over any port without the necessity of adding port mapping rules. If one computer runs FTP, Web, and Samba servers, and no other computers on the LAN have any public services, this might be the right option.

Apple calls this machine the default host; other gateway makers call it the DMZ host. You must share an IP address over DHCP and NAT for this option to be available.

Warning! If your base station has a public IP address, your default host is as exposed as if it were on the public Internet.

You should still use DHCP reservation to maintain the computer’s private address over time; see Reserved Addresses.

To set up a default host, follow these steps:

Launch AirPort Utility for Mac, select your base station, and click Edit.

Click the Network button, and then click Network Options.

Check the Enable Default Host At box, and enter the last number in the IP address for your default host (Figure 97).

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Figure 97: To set up an exposed computer, check Enable Default Host At and enter the private IP address’s last number.

Click Save and then click Update.

The base station restarts with the new settings in place.

Access a Base Station via iCloud

There’s one more way to gain remote access, but not to computers on your network. The Back to My Mac feature of iCloud lets you access your base station from a Mac, so long as the Mac is running at least 10.7 Lion. Back to My Mac makes a one-way connection from the base station to the Mac, allowing you to access a drive in a Time Capsule or drives attached via USB to either an Extreme or Time Capsule just as if you were on a local network (you can’t attach a drive to an AirPort Express). Likewise, you can configure any supported base station from AirPort Utility as if you were on the same network.

Note: Back to My Mac can also use iCloud as a conduit for connecting Macs separated across networks, creating a secure connection between the two computers that lets them appear to be on each other’s local network.

To enable Back to My Mac access for a base station:

Launch AirPort Utility for Mac, select your base station’s icon and click Edit, and then click the Base Station button.

In the Base Station view, you can enter one or more iCloud-affiliated Apple IDs (Figure 98).

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Figure 98: Entering an iCloud-associated Apple ID allows you to use AirPort Utility to configure the base station over the Internet.

Click the plus button, enter your Apple ID username and password, and then click Sign In.

Click Update to restart the base station with the new credentials.

Tip: If you enter your credentials incorrectly, after you restart your base station, the LED on the base station will be amber and an amber light will show in AirPort Utility beside the base station’s icon.

Now from a remote Mac where you’re logged in to iCloud with one of the Apple IDs set for that base station, you can:

Mount hard drives from an Extreme or Time Capsule: In the Finder, open any window and look in the Shared section of the sidebar. The base station should appear as a listed server. Select the server and click Connect As to enter the password you set for access. The available shared volumes appear. See Gain Access.

Configure the base station: Launch AirPort Utility. Click the Other menu in the upper left, and all the base stations connected to the same iCloud account as the Mac you are using appear in a list. Select and configure any base station just as you would any locally connected base station—even (as I did!) updating the firmware remotely.

Note: You can’t use Time Machine to back up to a remotely mounted AirPort Extreme or Time Capsule volume over Back to My Mac.

Set Up a Shared Printer

With a base station set up to handle local computers and hooked into the Internet, your next step may be to attach a printer to the base station so that it can be shared among all the local computers. In this chapter, I explain how to set up a base station for an attached printer using either a USB or a wireless connection, and how to Add a Shared Printer to a Mac and Add a Shared Printer in Windows 10.

Add a Printer with USB

Plug the printer into the base station (any AirPort model) or a USB hub (Extreme, Time Capsule). You should not need to reboot your base station for it to recognize the printer.

The AirPort Extreme and the Time Capsule each have a lone USB port that can connect to either a single printer or a single hard drive. Add a USB hub, and you can connect one or more printers and drives in any combination. (For maximum reliability and performance, I recommend a Hi-Speed powered hub with external AC power.) The AirPort Express is designed to connect to only a single USB printer, but not to an attached hard drive nor a hub.

Add a Wi-Fi Printer Using WPS

Wi-Fi–enabled printers that support Wi-Fi Protected Setup (WPS can use this simplified method to connect to connect to an AirPort network. WPS lets a device join a network securely once you tell the base station that the device wants to connect.

Before starting, check whether your printer has a PIN (this will be in the manual) or if it can connect automatically to any base station in range that offers a connection.

To make the connection:

Select a base station in AirPort Utility for Mac.

Choose Base Station > Add WPS Printer.

In the Add WPS Printer dialog (Figure 99), select PIN if your printer has a PIN or First Attempt if it will accept any available network. Click Continue.

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Figure 99: The Add WPS Printer dialog lets you pick how to connect a WPS printer to the network.

Depending on what you selected, you will see:

PIN: Enter the PIN provided, and click Continue.

First attempt: A dialog with a waiting spinner appears until the printer connects.

You may need to select the network from a menu on the printer.

If the connection is made, the printer will be available on the network.

Add a Shared Printer to a Mac

To add a shared printer to a Mac, make sure the printer is on and not in standby-power mode, and then use these steps:

Go to System Preferences > Printers & Scanners.

Note: These steps work specifically in 10.9 Mavericks through 10.11 El Capitan, but they should work okay back through 10.5 Leopard.

Near the bottom left, click the plus button to open the Add window (Figure 100).

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Figure 100: Choose the Bonjour-shared printer.

If needed, click Default at the top of the window to see the printers available over Bonjour.

Select the printer in the list. After a moment, the Mac should recognize the printer and display its driver in the Use pop-up menu, and note the name of the base station in the Location field. If the Use menu doesn’t fill in, choose the driver from the pop-up menu.

Click Add. Your Mac may automatically download printer drivers.

The printer should now be available from the Print dialog in your various Mac applications. If not, consult Troubleshoot an Unavailable Shared USB Printer, later in this chapter.

Tip: If you can’t make any of this work, buy the $20 Printopia, an OS X utility that lets you share a printer via AirPrint.

Add a Shared Printer in Windows 10

Windows 10 seems to recognize AirPrint-shared devices just fine. Here’s how to make the connection:

Open Settings.

Click Devices.

Click Add a Printer or Scanner.

While there are a ton of options, selecting “My printer is a little older. …” does the trick (Figure 101). Click Next.

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Figure 101: The Add Printer dialog lets you find “older” printers.

After a moment, Choose a Device or Printer to Add to This PC should appear (Figure 102). Select your printer and click Next.

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Figure 102: Your device should appear as an option.

A dialog appears that says Installing Printer. Click Close to complete the set up.

The printer is now available to all applications.

Note: For older versions of Windows, you can add Bonjour network resource discovery for Windows XP through Windows 8 with Apple’s free Bonjour Print Services for Windows package. However, Apple stopped updating it in 2010, thus it’s impossible to rely upon.

Troubleshoot an Unavailable Shared USB Printer

If you followed the directions earlier in this chapter and you still can’t print to your shared printer, one of the following suggestions should shed light on the problem:

Make certain that the printer is powered up, not in standby-power mode (which sometimes prevents an initial connection), and not in an error condition (such as out of paper or out of ink).

Check if the computer is on the same network as the base station. To do so, on the computer, launch AirPort Utility and see if the base station appears in AirPort Utility’s graphical network display with a green dot next to it. If not, use Quick Troubleshooting Guide to discover why.

Using AirPort Utility for Mac, select the base station and choose Base Station > Restart. Click Continue. (In AirPort Utility for iOS, edit the base station and then tap Advanced > Restart Base Station.) Once the base station has restarted, try again.

Look for advice in the Apple support article about USB printer troubleshooting. Note that the last suggestion, under “Still not working?” is to contact the manufacturer for more information, for instance, to confirm that the printer works with AirPort printer sharing.

Set Up a Shared USB Disk

The AirPort Extreme and the Time Capsule both add an interesting option to a network: they can share disks across a network without those disks being attached to a computer. Both models can accept one or more external drives plugged in via USB or via a USB hub; the Time Capsule also includes a non-removable internal drive.

Either model can share drives over a network with both the standard Apple Filing Protocol (AFP) format, the same format used with Personal File Sharing and OS X Server share files, and Samba, a network file-sharing service compatible with OS X, Windows, and Linux.

Attached hard drives can be accessed over the Internet via AFP using Back to My Mac, too (see Access a Base Station via iCloud.

In this chapter, I cover a handful of procedures for using the Time Capsule and the Extreme to share disks:

Read Prepare Your Drive, next, to find out about formatting and physically attaching drives.

Work with Time Machine covers setting up Time Machine backups as well as how to make a backup archive of a Time Capsule disk or to erase the disk.

Grant Access and Gain Access look at how users on the network can best access the disks.

Warning! You can’t share volumes via either only AFP or only Samba; you must share through both.

Note: The USB 2.0 port on the current AirPort Extreme and Time Capsule models has a maximum raw rate of 480 Mbps. This is out of date compared to USB 3 (5 Gbps) and 3.1 (10 Gbps). A 5 GHz network at top throughputs can almost match gigabit Ethernet, but a USB 2.0 drive will be poking along at a far lower rate.

Prepare Your Drive

The Time Capsule’s internal drive comes preformatted, so it should be ready to go, but it can be erased to its pristine state through AirPort Utility (see Erase, ahead).

Warning! Before you format anything, read Grant Access, ahead, to learn the quirks that can arise with different formats and different types of access.

You must format attachable disks before you connect them to the base station, using either the Mac HFS+ format, or the FAT16 or FAT32 (MS-DOS) formats. Each partition on a disk becomes a separately available shared volume. (FAT16 supports smaller maximum partition sizes than FAT32; you’re unlikely to see FAT16 except on disks formatted by very old computers.)

You can connect a single drive to the USB port on the Extreme or Time Capsule, or connect a USB hub and then a series of drives to the hub. The drives may be hard drives or USB thumb (flash) drives, but you cannot use CD/DVD drives with removable media.

Once one or more drives are formatted and connected, you can access them and let others access them, too. You handle all the limited configuration options in AirPort Utility in the Disks view.

Disks, Partitions, Volumes, Files, and Folders

Here’s a guide to file-sharing concepts you need to understand in order to make sense of this section:

Hard disk: A hard disk is a physical piece of hardware that contains data.

Partition: A partition is a division of a disk’s available storage into a separate logical compartment—part of the physical disk is written with certain kinds of data, and a disk-wide partition map is updated to reflect that partition information. Many disks have a single partition that spans the entire disk’s storage capacity. The partition’s format—like HFS+, FAT16, FAT32, or NTFS—determines how data is written to the disk; each operating system supports a different set of formats. (These are the only supported partition types: pure Unix won’t work, for instance.)

Volume: While volume is a synonym for any partition on a disk, I like to use shared volume to mean a shared partition that can be mounted over a network in the context of file sharing. A fileserver is a device that has one or more volumes available to share.

Files and folders: Any format you deal with stores files inside folders, the latter also known as directories. With some systems, you can share folders as volumes. In some cases, the base station makes folders into volumes, so that you can control access more finely, as described ahead.

View and Manage Connected Volumes

In AirPort Utility for Mac, select your base station, click Edit, and then click the Disks button. Each disk connected to the base station has its partitions noted in the Partitions list at the top (Figure 103). This list includes the name and the available space.

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Figure 103: AirPort Utility lists any disks’ partitions that are connected to a base station.

Tip: In AirPort Utility, you can rename a partition for a Time Capsule drive to give it a more descriptive name. Double click the name to make it editable.

If you click Update, choose Base Station > Restart, or unplug a base station, users connected to the base station as a file server will have their connection interrupted (Figure 104). All users on the network should unmount the base station’s volumes first, if possible.

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Figure 104: The Mac complains if you unplug or restart a base station with users connected to a shared disk.

When no users are connected, the drive is in a standby state that lets you unplug it from the Extreme or Time Capsule without harm, or turn off a Time Capsule without harming its internal drive.

Configuring a Base Station to Share with Back to My Mac

If you have one or more iCloud accounts activated for a base station, you will also see the checkbox Share Disks over WAN (Wide Area Network) on the Disks pane in AirPort Utility. If this box is selected, your drives are shared using Back to My Mac over the Internet and Bonjour over a local network, so long as any client Macs are logged in to the same iCloud account (Figure 105).

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Figure 105: On a Mac logged in to one of the same iCloud accounts as the base station, the AirPort Extreme shows up as a shared volume using Back to My Mac or Bonjour.

One of the most useful things about this feature is that it lets you turn a base station into a network-accessible fileserver both locally and remotely, thus avoiding having to keep a computer running all the time for that purpose.

Work with Time Machine

Once you’ve hooked your Time Capsule into your network or attached an external drive to either a Time Capsule or AirPort Extreme, you can configure the base station to accept Time Machine backups; I cover that procedure next. I also explain how to Erase a Time Capsule drive; external drives can’t be erased from AirPort Utility.

Time Machine Backups

The Time Capsule’s very name indicates that it has something to do with the Time Machine backup feature.

Note: You can back up with Time Machine from multiple Macs on a network to any internal or external Time Capsule drive. As for the AirPort Extreme, official support for backing up to attached volumes is available only for 802.11ac base stations, even though it may work with 802.11n models.

Warning! The first backup over Time Machine can take a very long time over Wi-Fi—even using 802.11ac—because Time Machine backs up all the files the first time. Subsequent backups copy only files that have changed in the interim. For the first back up, connect a Mac via Ethernet to a base station overnight.

To use Time Machine with a base station volume, follow these steps:

Go to System Preferences > Time Machine.

Click the Select Disk button.

A dialog appears, listing locally available base station drives (Figure 106). (Only HFS+ formatted drives, including the Time Capsule internal drive, show up.)

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Figure 106: Time Machine shows available disks attached to your computer and on the network.

Select the disk, and then click the Use Disk button.

Note: Backup encryption is an option only for Mac-connected drives.

Time Machine asks you to enter the password to mount the drive, if anything but Guest access with read and write has been selected. (Read Grant Access, a few pages ahead.) Enter that password and click Connect; the password is stored for future access.

Time Machine now proceeds with backups.

Keeping a Time Capsule in Trim

Time Capsule has two features unique to its internal drive that you should be aware of.

Disk Integrity

Every time that a Time Capsule powers up or restarts, it performs a quick integrity check on the internal drive to make sure it’s working as expected. Minor errors are automatically fixed, but if the drive can’t be repaired, the yellow light on the front of the Time Capsule flashes, and AirPort Utility launches on any computer on the local network. There’s little that you can do with a failed internal drive, however, except get a replacement if it’s under warranty, or find a third-party firm that can swap the drive.

Erase

If your internal Time Capsule drive becomes corrupted, or you want to remove its contents irretrievably—before selling the base station, for instance—the Erase feature is what you need.

Warning! During an erase operation, the Time Capsule locks out Time Machine backups and file server access to any volumes, internal or external.

To reset the contents of your Time Capsule’s internal drive:

In AirPort Utility for Mac, select your Time Capsule, click Edit, and click the Disks button.

Select the internal hard drive, which appears with a blue icon.

Click the Erase Disk button below the Partitions list.

In the dialog that appears, optionally rename the sole partition on the drive and/or choose an erasure method.

The choices in the Security Method pop-up menu range from smart to insanely paranoid. A 7-Pass Erase should provide security from all but national security agents. If you’re erasing the drive to sell it, I suggest Zero Out Data; if you’re erasing it for your own purposes to re-use, choose Quick Erase (Figure 107).

Warning! Choosing 7 or 35 passes could make the erasure take many, many, many hours to complete.

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Figure 107: You can go to rather extreme extremes to secure the erasure of your internal drive.

Click Erase.

You’re prompted to make sure you really want to erase the drive. Click Continue to proceed.

Grant Access

Apple offers little granularity in setting up security and access for disks that are connected to an Extreme or Time Capsule. You can pick only one of three methods for setting passwords, and you can’t set permissions individually for folders or files on each disk, nor set permissions differently for different partitions or different disks.

AirPort Utility has three ways to grant access, found in the Disks view in the Secure Shared Disks pop-up menu (Figure 108).

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Figure 108: AirPort Utility offers three options for securing a shared disk by controlling the level of security.

The three ways to grant access are:

With accounts: On partitions formatted with HFS+, you can specify individual usernames and passwords, each with different levels of access; these accounts are distinct from any Mac or Windows user accounts on the computer that’s configuring the base station. An Accounts list appears through which you can add, edit, and remove users. User access options can be set as Read and Write, Read Only, and Not Allowed. (That last option lets you disable an account without removing it.)

With a disk password: This password controls access to all disks; it is distinct from the base-station password and network encryption password. All users who can access the disk have access to all files. This works for a small network where you want to make sure that people who have fileserver access can’t modify the base station, even unintentionally.

With device password (default): This self-explanatory option means that only a single password is used to secure both the base station’s settings and any attached drives. This option is good for home and small networks in which you’re not concerned about someone who knows the disk-access password also changing the settings on a base station. (If you use the default setup, this password is also the same as the network encryption password for WPA or WPA2.)

Gain Access

The Extreme and Time Capsule offer file sharing with the standard methods: AFP, commonly known as AppleShare, and Samba, the default Windows method. Users on the network can access base station file servers connected to an Extreme or Time Capsule via normal file-sharing options, such as selecting the server from a Finder window sidebar in the Shared section.

With a base station or disk password, the contents of all partitions are available when a partition is mounted.

With accounts, however, the options vary by partition type:

With an HFS+-formatted partition:

A folder named with the account is created on only one partition, no matter how many HFS+ partitions are attached; users mount this folder as a volume having the account name.

A folder named Shared is also created on one partition, and users mount it as a volume named with the partition name.

Any other partitions are served as volumes named with the partition name.

With a FAT 16/32-formatted partition: A folder named Shared is served. Users mount it as a volume having the partition name.

The base station’s fileserver shares any HFS+ volumes only as AFP volumes, while Samba can share either HFS+ or FAT32 (MS-DOS) formatted partitions as SMB/CIFS volumes.

Mount on a Mac

You can mount the base station server and disks through the Finder, just like any other network volume. Open any Finder window, and look in the sidebar’s Shared section for a list of servers.

The sidebar shows any servers on the local network with AFP volumes available for mounting, as well as FTP servers that use Bonjour to advertise their availability. If you are set up to Access a Base Station via iCloud from that Mac, you’ll also see any available base station(s) in that list.

To mount a volume from one of these servers, follow these steps:

Select the server name in the Shared section of the sidebar.

Click the Connect As button in the upper right, enter your credentials, and click Connect (Figure 109).

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Figure 109: The Mac knows that just a password is needed to connect to a base station’s file-sharing service.

OS X is clever enough that for Extreme and Time Capsule shared drives that use just a password for access—not a user account—it prompts you only for that password.

Double click a volume that’s shown in the mounted server window to mount it on your system.

Unmounting

To unmount a network volume, select the volume on the Desktop and press Command-E, or choose File > Eject “volume name.” Or, to unmount all volumes associated with a server, in a Finder window sidebar, click the Eject icon by the server’s name, or in the server’s Finder window, click Disconnect.

In 10.6 Snow Leopard and later, a disk icon turns gray while Mac OS X removes its associations; it disappears when the process is complete. If a file is in use by an app, the Mac tells you which one.

Mount in Windows 10

In Windows 10, follow these steps:

Use AirPort Utility to determine the local network IP address of the base station, which will be something like 10.0.1.1.

Click the Windows menu and launch the File Explorer.

In the location field, enter \\ plus the IP address (like \\10.0.1.1) and press Enter.

In the Name field (Figure 110):

If you don’t have a user account because the base station has a base-station or disk password, enter any short bit of text or leave the field blank.

If you have a user account name, enter it.

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Figure 110: Enter your credentials to log in.

In the Password field, enter the base station, disk, or account password.

Select the volume or volumes you want to mount, and click OK.

To unmount a disk, find the volume under My Computers or on the desktop, right-click the volume, and select Disconnect.

Connect with a Personal Hotspot

Every iPhone and every “Wi-Fi + Cellular” iPad has, in addition to a Wi-Fi radio, a built-in data modem that lets the device access high-speed mobile data networks. The logical question in the iPhone’s early years was: why can’t we use that same modem with our laptops (or other devices) when we’re traveling instead of having to buy a separate cellular modem or router and pay a separate monthly service fee?

Fortunately, Apple followed the suit of other smartphone makers and added Personal Hotspot, an iOS feature that lets you use your phone or tablet as a hotspot conduit to the mobile Internet. While “Personal Hotspot” implies a Wi-Fi hotspot connection, which is one component of it, you may also use Bluetooth or USB to extend access to other devices. All three methods may even be used simultaneously.

Personal Hotspot’s availability varies by carrier, although operators around the world offer it: consult this list by Apple to check on yours. In North America, all carriers in the United States and Canada allow its use except for two tiny ones in Canada.

In the United States, the four largest carriers all include mobile hotspot use in their current plans, and count bandwidth consumed just as they do any other data used by an iPhone or iPad.

Note: All iOS 8-capable iPhones and Wi-Fi + Cellular iPads can enable every Personal Hotspot option. This wasn’t always the case with previous versions of iOS in conjunction with certain iPhones and iPads. But it’s no longer an issue.

Note: In this chapter, I talk about a “mobile hotspot” or “Personal Hotspot” to refer to all the features, but I use the term “tethering” when the discussion is specifically about Bluetooth or USB.

In this chapter, I first discuss how to turn your iOS device into a personal hotspot and then I talk about how to Connect to a Personal Hotspot.

Turn On Personal Hotspot

There are two ways to turn on the Personal Hotspot feature: directly on your iOS device or through another computer or iOS device.

Warning! Devices that connect to a Personal Hotspot network typically don’t treat it any differently than a regular Wi-Fi or Ethernet network—which can make it easy to rack up huge amounts of usage. You will want to pause or disable sync services, like Dropbox, and online backup systems, like Backblaze or CrashPlan. You may also want to avoid using any streaming video services or digital media downloads while connected via a Personal Hotspot.

Directly in iOS

To turn your iOS 8 or 9 device into a personal hotspot:

Open the Settings app and tap Cellular Data (iPad) or Cellular (iPhone).

Tap Personal Hotspot to open the Personal Hotspot screen.

Switch the hotspot on and Set a Wi-Fi Password. The screen is also full of connection information (Figure 111).

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Figure 111: You can connect to Personal Hotspot in several ways.

After you turn on the Personal Hotspot switch, Personal Hotspot appears as an option on the Settings app’s left pane (iPad) or main screen (iPhone) so you can access it quickly.

Note: To continue setting up the hotspot, skip ahead a few pages to Set a Wi-Fi Password.

From Another Device

In order to turn on Personal Hotspot through another device, both devices must support Instant Hotspot, a feature that lets you turn on Personal Hotspot from another device. For example, you could turn on your iPhone’s personal hotspot from your Mac, without even touching the iPhone. (Instant Hotspot is part of Continuity, a set of features that make connections between your Apple devices.)

Instant Hotspot Requirements

Instant Hotspot has a host of specific hardware, software, and networking needs:

The hotspot device must be running iOS 8.1 or later. It must also have been released in the last 2–3 years. (See Apple’s complete list.)

If you’re invoking Instant Hotspot on a Mac, that Mac must be running 10.10 Yosemite or later. The Mac must also be a model released in mid-2012 (MacBook Air and MacBook Pro) or later (Mac Pro, Mac mini, and iMac).

If you’re invoking Instant Hotspot from an iOS device (such as a Wi-Fi–only iPad), that device must be running iOS 8.1 or later and have been released in the last 2–3 years. (See Apple’s complete list.)

Both devices must be signed in to the same iCloud account.

Both devices must have Bluetooth enabled.

Warning! In my experience, Instant Hotspot worked sporadically and unpredictably in Yosemite and iOS 8. I was pleasantly surprised to find that it works much more frequently in El Capitan and iOS 9. However, even when every criteria exists, I still don’t always see an instant hotspot in my OS X Wi-Fi menu—and I’ve not yet found a way to fix the problem.

Once you’ve ensured that your devices meet all the requirements—including signing in to the same iCloud account, connecting to the same Wi-Fi network, and turning on Bluetooth—you can turn on Instant Hotspot:

Mac: From the Wi-Fi menu, under Personal Hotspot, choose the device (Figure 112).

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Figure 112: Instant Hotspot puts an iOS device in the Wi-Fi menu in OS X. In this case, the iOS device is called Executive Privilege.

Another iOS device: In Settings, tap Wi-Fi and tap the device in the Personal Hotspots list (Figure 113).

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Figure 113: In iOS, pick a device from the Personal Hotspots list.

Even if you’re not planning to connect, you can see the battery life, signal strength, and connection strength of your iOS device as a compact set of graphics in the menu or list.

Set a Wi-Fi Password

When you first turn on Personal Hotspot, iOS creates a strong WPA2 password. To connect a device over Wi-Fi to the hotspot, you must enter this password on that device.

The default password created by your iOS device is sometimes a sequence of recognizable words and numbers; other times, it may appear to be random. (At one point, the difference seemed to be by carrier, but now it’s impossible to tell.)

You can’t decide not to use a password at all, but you may compose your own. You have to pick one that’s eight characters or more, although you can make that 12345678 if you must. Tap to enter your password.

For this kind of connection, where it’s not a base station in a fixed location that someone might try to access, I suggest thinking of an eight- or nine-letter word and adding two punctuation marks to the end, like memorable?%.

Extra Security with Personal Hotspot

Using USB, Bluetooth, or Wi-Fi to connect to a hotspot device provides a strong layer of security around your connection, which is re-assuring if you’re at a location like a coffee shop, where the network may not be well secured. USB is a physical connection and can’t be monitored. Bluetooth has its own strong automatic security. Apple’s required use of WPA2 Personal for Wi-Fi ensures protection there, too.

You can also typically avoid the necessity of a public virtual private network (VPN) when you use Personal Hotspot because of the high security of a mobile broadband network compared to that of a typical Wi-Fi network in a coffee shop. Public VPNs, of which there are many available, secure the connection from your device out to a data center. A carrier’s mobile network is equally good for the same sort of protection against people on a local network sniffing your data.

Name Your Wi-Fi Network

The Wi-Fi network has the same name as your iOS device. This is typically your name, or that of whichever account you used to set up the iOS device (Figure 114). If you don’t feel like broadcasting your account name when you turn on Personal Hotspot, you can change it.

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Figure 114: The Wi-Fi network name (left) is identical to the name of your device, which you can see in iTunes (right) or in Settings.

To change the name, visit Settings > General > About > Name and enter a new name. Or, with the device connected to iTunes via either USB or Wi-Fi, click the device’s icon in the top bar in iTunes, and then click its name to select it, which highlights the name. Type a new name, and press Return.

You need to turn Personal Hotspot off and back on for the new name to be broadcast.

Consider Turning off Certain Radios

Now that you’ve turned on Personal Hotspot, you might not want it to be available through Bluetooth or Wi-Fi, because nearby devices of yours might accidentally connect to it. The only way to prevent a connection from a device with the right credentials is to turn off the Bluetooth or Wi-Fi radio on the hotspot device.

Warning! Disabling radios turns off networking features, including OS X Continuity features and, in the case of an iPhone, any Apple Watch connection.

To turn off Bluetooth, tap Settings > Bluetooth and turn off the switch. To disable Wi-Fi, tap Settings > Wi-Fi and turn off the switch. With either or both Bluetooth and Wi-Fi turned off, the Personal Hotspot feature pops up a warning when it’s switched on (Figure 115).

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Figure 115: If any networking type used with Personal Hotspot is off, iOS prompts to turn it on.

You can also change the personal hotspot’s Wi-Fi password to prevent devices that previously connected from gaining access again (see Set a Wi-Fi Password, slightly earlier).

Connect to a Personal Hotspot

With Personal Hotspot on, you have three choices for how to connect:

Wi-Fi: Any Wi-Fi–equipped device can connect just as if the iOS device were a wireless router. Up to five devices can connect via Wi-Fi. (Verizon and Sprint used to limit this to three, but that appears to be lifted.)

USB: Plugging your computer into your iPhone or iPad gives you a high-speed data connection that you know works as long as the cable isn’t bad. The downside? Being literally tethered.

Bluetooth: This method requires more steps to make a connection initially, but it gives you cable-free flexibility. Most Bluetooth-equipped devices can connect through this method, including iPhones, iPod touches, and iPads. No more than three devices may connect via Bluetooth at the same time.

Tip: Wi-Fi can use more battery power than Bluetooth, so you might opt for Bluetooth tethering. However, the data rate isn’t stellar: Bluetooth 4.0, found on the iPhone 4S and later and on the 3rd-generation or later iPad, has a raw data rate of 3 Mbps for continuous connections, and an effective throughput of 2.1 Mbps. That’s far below GSM 3G/4G rates and well below LTE rates.

There is a maximum of five total connections across all these methods. If you have five devices connected and try to connect another, the connection will be refused.

I explain how to make a connection shortly; for now, I want to mention that once you make a connection, a blue pulsing banner appears across the top of the iPhone or iPad screen (Figure 116).

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Figure 116: A banner lets you know if your device is acting as a cellular modem for a computer via USB, Wi-Fi, or Bluetooth.

The banner shows the number of devices connected, too.

If the phone or iPad is on standby, a smaller status banner appears on the Lock screen when you wake it (Figure 117).

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Figure 117: The Lock screen also shows whether the hotspot is active, with a tiny superscript numeral revealing how many clients are connected.

Note: Windows computers, Android phones, and other devices can also connect via Wi-Fi; many devices can also connect via Bluetooth; and Windows at least can also tether via USB. The process is identical on those platforms to hooking into a Wi-Fi, Bluetooth, or USB shared network, and it neither needs special software nor displays any special indicators as in iOS and OS X.

Access via Wi-Fi

Using Wi-Fi to connect to a Personal Hotspot network is the easiest case because no special setup is required. You use whatever method you normally employ to connect to a Wi-Fi network from the device, and I provide directions for several common operating systems just ahead. The name of your iOS device is the name of the Personal Hotspot network.

Connect via Wi-Fi in OS X

In OS X, you can use the Wi-Fi menu to select the Personal Hotspot network by name:

Open the Wi-Fi menu to see a list of available networks.

Choose the network’s name:

In 10.10 Yosemite or later, if it’s an iOS 8.1 (or later) hotspot, it appears as an Instant Hotspot network. The menu item shows the cellular connection type, battery level, and signal strength (Figure 118). (If Personal Hotspot is not active on the device, choosing the hotspot in the Wi-Fi menu turns it on.)

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Figure 118: Select the hotspot under Personal Hotspot. In this case, you’d choose Executive Privilege.

If you are using 10.9 Mavericks or earlier or if the hotspot device is running iOS 8 or earlier, a personal hotspot network shows up in the main list of networks with a linked-chain icon just to the left of the signal-strength icon (Figure 119).

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Figure 119: If a hotspot is set up on a device running iOS 8.0 or earlier, or if the Mac is running 10.9 Mavericks or earlier, the hotspot’s network name appears in the Wi-Fi menu’s networks list.

Enter the password, and click Join.

Note: If you leave Remember This Network checked, you won’t be prompted in the future for the password. The flip side of that benefit is that it’s difficult to prevent future automatic connections when the Personal Hotspot Wi-Fi connection is active.

You’re now connected. Your Mac will stay connected as long as the Personal Hotspot feature is active. The next time you turn on Personal Hotspot, your Mac will reconnect if you stored the password and if your Mac isn’t already associated with a Wi-Fi network.

Disconnect from a Personal Hotspot

To stop using a personal hotspot over Wi-Fi, hold down the Option key and open the Wi-Fi menu. Choose Disconnect From Network Name and your link is severed. (In Yosemite and later, the Disconnect item appears even if you don’t hold down the Option key whenever the Mac is connected to an iOS Personal Hotspot network.)

Don’t Auto-join in the Future

To prevent the Mac from connecting automatically in the future, follow these steps:

Go to System Preferences > Network.

Select Wi-Fi in the list at left.

Click the Advanced button.

From the Wi-Fi pane, select the Personal Hotspot network and then click the minus button to delete it.

Click OK and then click Apply.

Connect via Wi-Fi in iOS

In iOS, you use the Settings app to connect to a Personal Hotspot.

If both devices are running iOS 8.1 or later:

Tap Settings > Wi-Fi.

Choose the network from the Personal Hotspots list (Figure 120).

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Figure 120: Look for the chain icon in the Personal Hotspots section.

Enter the password when prompted.

Your device is now connected. The chain icon appears at the left of the iOS status bar instead of the normal Wi-Fi icon.

If either device is running iOS 8 or earlier:

Tap Settings > Wi-Fi.

Choose the network from the list. Personal Hotspot networks are shown with a special chain icon in iOS 4.3 and later.

Enter the password when prompted.

You are now connected. The chain icon appears at the left of the iOS status bar instead of the normal Wi-Fi icon.

Control Automatic Reconnection

As long as the password is stored for the iOS network and isn’t changed, your iOS device will reconnect automatically whenever it’s in range and the Personal Hotspot Wi-Fi connection is active. To stop using the mobile hotspot right away, choose another network from the list or turn off the Wi-Fi adapter.

If you want to prevent connecting automatically in the future, while the hotspot connection is active, tap the blue info button next to the network name and then tap Forget This Network. This removes the network’s stored setting and disconnects the device from the Personal Hotspot network immediately.

Disable Wi-Fi Sharing in iOS

To turn off the hotspot on the device that is sharing its connection, just tap Settings > Personal Hotspot and then turn off the Personal Hotspot switch. Or, you can tap Settings > Wi-Fi and turn off Wi-Fi entirely.

You can also block all existing connections from client devices by changing the Wi-Fi password on the Personal Hotspot screen. This will also prevent devices with a stored password from reconnecting automatically or manually until you provide the changed password.

Tether with USB in OS X

With Personal Hotspot enabled, connect your hotspot device to your computer with a USB cable. The first time you enable Personal Hotspot and plug the device in to a Mac via USB, OS X alerts you that the interface is added and the Mac’s Network system preference pane adds an adapter entry (Figure 121).

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Figure 121: An entry appears in the adapters list.

OS X automatically activates a tethered link and turns that red dot green.

Note: If you’re not seeing this, you may need to launch iTunes the first time you tether. iTunes doesn’t seem to have anything to do with USB tethering except initial activation.

To halt the active USB tethering connection, disconnect the USB cable. Alternatively, you can disable the iOS adapter profile. In the Network system preference pane, select the iPhone USB or iPad USB adapter, and then from the gear pop-up menu, choose Make Service Inactive. Click Apply in the lower-right corner.

Tether with Bluetooth

On your hotspot device, make sure Bluetooth is turned on: swipe up from the bottom to show Control Center and check that the Bluetooth icon is active. If it’s not, tap it. (You can also manage Bluetooth from the Settings app.) Once you’re sure it’s enabled, you can make a Bluetooth connection from OS X or iOS, as I describe next.

Bluetooth uses less power than Wi-Fi, almost nothing in standby mode, so a Bluetooth connection could allow both an iOS device and a paired piece of hardware to work longer without AC power.

Connect with Bluetooth in OS X

Follow these steps to set up a Bluetooth connection between your hotspot device and a Mac running Yosemite or later (instructions are substantially different in earlier versions of OS X):

Go to System Preferences > Bluetooth.

Your iPhone or iPad appears in the list of devices (Figure 122). (If it doesn’t appear, check that Bluetooth is enabled on the iOS device and that it’s within a few dozen feet of your computer.)

Click Pair.

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Figure 122: Initiate pairing from OS X.

A pop-up dialog appears with a 6-digit code. On the iOS device, a similar confirmation dialog pops up (Figure 123).

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Figure 123: The Mac and iOS device both display the same code.

Confirm that the code is identical, in order to prevent a s0-called man-in-the-middle attack with someone nearby trying to intercept the connection. (That’s very unlikely, but it could happen.) The additional cue is the name of the device. Tap Pair on the hotspot device.

On the Mac, your iOS device appears in the list (Figure 124).

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Figure 124: The device is paired in OS X and connected.

Now, in System Preferences, click Show All, then select Network.

In the adapters list at left, you’ll notice a new Bluetooth PAN entry; PAN stands for Personal Area Network, and it’s the kind of network that Bluetooth creates. Your device should be selected in the Device pop-up menu (Figure 125). Click Connect.

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Figure 125: The Network preference pane lets you manage the connection over USB.

On the Mac, you see the Status label set to Connected as shown in Figure 125, above, and if the Bluetooth system menu icon is showing, it will have dots bisecting it horizontally. On your hotspot device, the Internet tethering banner appears.

To disconnect Bluetooth tethering, you can do any of the following:

In the Network preference pane, with Bluetooth PAN selected in the adapters list, click the Disconnect button.

On your hotspot device, in Settings > Personal Hotspot, turn off the Personal Hotspot switch.

Turn off Bluetooth networking. In iOS, tap Settings > Bluetooth; on the Mac, look in the Bluetooth system preference pane or the Bluetooth menu on the menu bar.

Connect with Bluetooth in iOS

Although all iOS devices have Wi-Fi built in, Bluetooth consumes less battery power and may be a more appropriate choice. You can easily set up a Bluetooth connection between a hotspot and any iOS device running iOS 4.3:

Tap Settings > Bluetooth.

If Bluetooth is off, tap the switch to turn it on.

Tap the Personal Hotspot name in the list of Devices (Figure 126).

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Figure 126: The personal hotspot appears in the Devices list; here, it’s “Executive Privilege.”

Both devices show confirmation dialogs (Figure 127).

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Figure 127: Tap Pair on both devices to proceed.

If the codes match, tap Pair on both devices.

The iOS device is now connected over Bluetooth, and a chain icon appears at the left of the status bar instead of the normal Wi-Fi icon.

To disconnect from the hotspot, you can do either of the following:

On the connected device: Slide the Bluetooth’s switch off.

On the hotspot device: Turn off the Personal Hotspot feature or turn off Bluetooth.

To reconnect, open Settings > Bluetooth and then tap the name of the Personal Hotspot in the Devices list.

You might want to discard a stored Bluetooth pairing from the Devices list if, for instance, you’re using a friend’s device or you don’t want someone else using your iOS device with the paired connection. To remove the pairing, tap the info button next to the device name and then tap Forget This Device.

Using Bluetooth to Tether an iOS Device to a Laptop

A side benefit of the capability to tether over Bluetooth is that you can use your iOS devices to grab Internet access from a laptop. For instance, if you’re in a hotel or other location in which you have to pay for each device you connect to a Wi-Fi network, you were previously out of luck in relaying an Internet connection from a laptop to an iPhone, iPod touch, or iPad. Now you can.

On the Mac, use the Sharing system preference pane’s Internet Sharing option to share the Wi-Fi connection via Bluetooth PAN. Choose Wi-Fi from the Share Your Connection From pop-up menu, and select the Bluetooth PAN box in the “To computers using” list (Figure 128). Then select the box next to Internet Sharing in the Service list at left.

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Figure 128: You can share your Wi-Fi connection via the Bluetooth PAN to iOS devices.

If you don’t see Bluetooth PAN in the “To computers using” list, open the Network preference pane. Click the plus button at the bottom of the adapters list, and choose Bluetooth PAN from the Interface pop-up menu. Click Create, then click Apply. When you return to the Internet Sharing option in the Sharing preference pane, Bluetooth PAN will be there.

Share Files with AirDrop

Have you ever wanted to swap a file between a couple of your own computers without setting up file sharing and mounting a volume? Or pass a file to a friend or colleague without joining a common Wi-Fi network, setting up ad-hoc networking, or emailing it?

AirDrop is a solution to that common problem. Added in 10.7 Lion and iOS 7, the feature lets you find and share files with other users near you. Unfortunately, it took until 10.10 Yosemite for AirDrop to work between iOS and OS X! And there remain some differences and complications as I discuss below. However, it’s a remarkably nifty way—when the right hardware is available—to hand files back and forth.

In this chapter, I explain how to Configure AirDrop and how to Share with AirDrop.

Note: AirDrop works with iOS 7 or later on the iPhone 5 and later, the 4th-generation iPad or later, the original iPad Air and iPad mini and later; and the 5th-generation iPod touch or later. Macs must be models released starting in 2008; see Apple’s support page for AirDrop for specific models.

Note: To use AirDrop between iOS and OS X, the Mac must be running Yosemite or later and be a model introduced in 2012 or later. Bluetooth and Wi-Fi must be enabled on both devices, but they don’t have to be on the same Wi-Fi network. Read more under the System Requirements heading on Apple’s support page for AirDrop.

Configure AirDrop

With AirDrop, you have essentially just one choice to make, and that’s a choice about who can “see” you in the vicinity of your device’s range. You can pick that no one sees you, effectively disabling it; that everyone does; or that only AirDrop users whose identity matches something in your Contacts can spot you.

Note: Using Contacts requires that both parties are signed in to iCloud.

Configure AirDrop in iOS

There’s only one set of choices to make (Figure 129):

Swipe up to show the Control Center.

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Figure 129: The Control Center is where you set AirDrop access.

Tap the AirDrop area in the bottom left.

Tap an option (Figure 130):

Off disables AirDrop.

Contacts Only shows your device only to people whose email address is in your Contacts. This is the default option.

Everyone lets anyone on the local network see that you’re available to receive files.

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Figure 130: Pick how AirDrop advertises itself on a network.

Configure AirDrop in OS X

OS X has pre-2012 and 2012-and-later configuration differences.

Macs released starting in 2012 that have Yosemite or later installed have the same Off, Contacts Only, and Everyone options as iOS:

In the Finder, choose Go > AirDrop (Command-Shift-R).

At the bottom of the window, you can choose Off, Contacts Only, or Everyone from the Allow Me to be Discovered By pop-up menu.

Mac models released from 2008–2011 have no restrictions: any other Mac capable of interacting with it will see it, but only while an AirDrop window on that older Mac is open.

What Makes AirDrop Tick

AirDrop uses a combination of Bluetooth and Wi-Fi to work without the requirement that two devices are on the same Wi-Fi network. Bluetooth handles signaling and discovery.

A mode of Wi-Fi known by the trade name of Wi-Fi Direct enables direct device-to-device file transfers without dropping them off any Wi-Fi network to which they’re connected for Internet and local network access.

Share with AirDrop

In iOS, AirDrop is always associated with an app or file type: you share from apps, and received items are either opened with apps, opened as a URL, or stored as a photo. Yosemite and later can send and receive any kind of file or item.

Share with AirDrop in iOS

AirDrop is available in any Share sheet in iOS 7 and later: you can send URLs, files, photos, contacts, and more. When you tap a Share icon, AirDrop will appear at the top of the sheet, whether or not you’ve turned off discovery in Control Center. You’ll see a list of all devices on the local network that make themselves discoverable to everyone, or that match with your Contacts (Figure 131).

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Figure 131: The Share sheet shows all available AirDrop users.

To share over AirDrop, open the appropriate app and/or item and then tap the Share icon and select the user. The recipient will either automatically receive or tap or click to accept or reject the file, as described below.

When a file or other item is accepted or received, the label Sent appears on the icon for the person to whom you transmitted the item (Figure 132).

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Figure 132: The Sent label appears to confirm delivery.

Share with AirDrop from Yosemite and El Capitan

If you’re working in Yosemite or El Capitan in an app that has a Share sheet option, such as Safari or Photos, you can share directly from that app. Click the Share icon and choose AirDrop, and you can pick a recipient for a URL, image, or other item (Figure 133).

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Figure 133: You can AirDrop an item within an OS X app, too.

Alternatively, to share from the Finder, follow these steps:

In the Finder, choose Go > AirDrop (Command-Shift-R) or click the AirDrop item in a Finder sidebar window. The AirDrop window shows all available recipients (Figure 134).

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Figure 134: A list of recipients is shown in the AirDrop window.

Drag a file, folder, or set of items onto a recipient’s icon.

The recipient is prompted to accept the files. If she agrees, the files are transferred.

Note: If you’re using a 2012-or-later Mac with Yosemite or later and an older Mac with AirDrop support isn’t shown, click Don’t See Who You’re Looking For and then click Search for an Older Mac. An AirDrop window must be open in the Finder on that other Mac.

Receive a File in iOS

In iOS, you’re asked whether or not to accept the AirDrop transfer (Figure 135) when the same iCloud account isn’t logged in to the sending device.

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Figure 135: If the sending device is using a different iCloud account, you’re prompted to accept the incoming file.

For iOS devices logged in to the same iCloud account, files are simply accepted without any prompt (Figure 136).

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Figure 136: With the same iCloud account, incoming files just arrive.

If you tap Accept or are using the same iCloud account:

Image files are added to your Photos collection, the Photos app is launched, and the image is opened.

URLs are opened in Safari.

Other files are opened by the appropriate app, or an Open In control appears from which you can select the appropriate app.

Receive a File in OS X

In OS X, the AirDrop receiving procedure depends on the age of the computer, its operating system version, and whether the sender and recipient are logged in to the same iCloud account.

With a 2012-or-later Mac and 10.10 Yosemite or later installed:

Same iCloud account: The file, URL, or other item is received automatically. If it’s a URL, the Web page is opened. A small notification appears and a punctuated chime sounds (Figure 137).

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Figure 137: OS X automatically accepts files from iOS devices signed in to the same iCloud account. Progress is shown as a colored circle that fills the avatar’s circumference.

Any other user: The recipient is asked to Save, Decline, or Save and Open a file (Figure 138).

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Figure 138: In this case, shown on the sender’s computer, the recipient declined the file.

With 10.7 Lion through 10.9 Mavericks on any AirDrop-capable Mac:

The AirDrop window must be open in the Finder to receive files. When there is an incoming file, the recipient is asked to Save, Decline, or Save and Open a file.

Secure Your Network

If you use a wired network in your home, someone would have to break into your house, plug into your Ethernet switch, and then crouch there in the dark to capture data passing over your network.

Wireless networks have no such protection: anyone with an antenna sensitive enough to pick up your radio signals can eavesdrop on traffic passing over your network. This could be a neighbor, someone in a parked car, or a nearby business. Many free, easy-to-use programs make this a simple task for only slightly sophisticated snoopers.

However, you’re not powerless to prevent such behavior. Depending on what you want to protect and whom you’re protecting against, you can close security holes with tools that range from a few settings up to industrial-grade protection that requires separate servers elsewhere on the Internet.

Simple Tricks That Don’t Work

You may have read suggestions for setting up basic security that advise you to hide your network’s name and make it hard to connect to. In practice, this doesn’t work.

In a closed network, the base station stops broadcasting its network name, or SSID (Service Set Identifier), as part of its beacon, an “I’m here” message that access points regularly transmit in order to help clients connect to them. However, the beacon continues to be sent because it still includes information that is used for network data synchronization.

An open network appears by name in the Wi-Fi menu and in other places in a device’s interface that show the names of networks you can connect to. But closing the network makes it only slightly obscure. A cracker can easily find out that the network exists, and by monitoring for a connection or using a tool to create a disassociation for a computer on the network—which forces that computer to reconnect—the cracker can grab the network’s name. So you cannot rely on closing your network for any real security.

Although I discourage bothering with a closed network, here’s how to set one up:

In AirPort Utility (Mac or iOS), select and edit your base station, and then:

On a Mac: Click the Wireless button and then the Wireless Options button; then select the Create Hidden Network checkbox.

In iOS: Tap Network, and then turn on the Hidden Network switch.

Update the base station:

On a Mac: Click Save and then click Update.

In iOS: Tap Done repeatedly to reverse through a few configuration screens and then tap Update.

Wait for the base station to reboot.

Timed Access Control

Apple used to offer a way to limit access to devices by their MAC address, a unique identifier set for every network adapter. While this feature was removed, AirPort Utility does retain Timed Access Control (in the Network view) to limit devices to access the network on specific days of the week during specific hour ranges. You set access for a device by its MAC address (see Appendix D: What and Where Is a MAC Address?).

The feature can be useful if you’re trying to keep your kids (or spouse?) from using the Internet except during certain hours, but I find that it is too fussy to recommend, and the same settings must be re-entered on every base station on a network. It also doesn’t restrict plugging in via Ethernet.

Use Built-in Encryption

For a real defense, you must use password-protected encryption. Wi-Fi has always offered some form of built-in encryption to secure the connection between a client computer or device and the base station; this connection is the most vulnerable part of a wireless network.

Note: The connection from the base station to the rest of the network or the Internet must be secured separately from the Wi-Fi segment. Some people use virtual private network (VPN) connections to secure a larger chunk of their traffic.

Encryption always requires a key. With Wi-Fi encryption, you don’t enter the key directly, but instead enter a password that the system uses to generate or retrieve a key. Sharing the password reduces security by allowing others to see the same network traffic.

Three different encryption methods have been offered since 802.11b started appearing in hardware in 1999, each of which supersedes the previous one.

Wait, Where’s WEP?!

WEP (Wired Equivalent Privacy) was Wi-Fi’s first encryption standard and the only option from 1999–2003. It was almost intentionally designed to be weak. It had to work on the slow silicon of the day, and couldn’t be too robust due to issues surrounding U.S. export policies related to encryption.

Starting over a decade ago, effective attacks rendered WEP protection essentially useless, and it was abandoned beginning in 2003 with WPA and then in 2004 with the full-fledged WPA2. The only encryption that may be used with 802.11n and 802.11ac networks is WPA2. Every Wi-Fi adapter released starting in 2003 included or could be upgraded to use WPA2. (A lot of point-of-sale systems continued to use WEP until recently—some still do!)

Apple persisted for the longest time in allowing only WEP encryption for ad hoc computer-to-computer networks (a special Wi-Fi mode) and in the software base station mode available by sharing a networking connection in the Sharing system preference pane. Finally, in 10.8 Mountain Lion, Apple let the software base station use WPA2, but had a hidden Option-click trick to bring up WEP.

Yosemite killed WEP once and for all. Ad hoc networking offers only unencrypted connections, which I can recommend only if there are no other computer users in your vicinity. There is now no way to prevent someone from joining an ad hoc network or sniffing the traffic passing by. Use other approaches to sharing files, like AirDrop or Dropbox. The software base station now exclusively offers WPA2 (see Appendix B: Setting up a Software Base Station).

I think users have had enough time to make the transition.

WPA and WPA2 Background

WPA (Wi-Fi Protected Access) was released in 2003 by the Wi-Fi Alliance as an interim measure when work by an IEEE committee—802.11i—was taking too long. WPA is considered to be quite strong and was designed to allow even the earliest Wi-Fi gear to be upgraded to support it. The original AirPort Card can use WPA with 10.3 Panther or later. (The original 802.11b AirPort Base Station can’t be upgraded.)

WPA2 was the final version of WPA security that includes all the work done in the 802.11i committee. WPA2 replaces the weaker WEP key with a government-grade method favored by corporations. Any equipment released in 2003 or later can handle WPA2. All Apple base stations released starting in 2003 handle WPA2, but 10.3 Panther or later is required to use it.

Warning! The original AirPort Card (found in pre-2003 Macs) cannot access WPA2-protected networks.

The Key to Keys

WPA2 is a more robust version of WPA, which it replaced. WPA supports just one new encryption method that’s a repaired version of WEP, known as TKIP (Temporal Key Integrity Protocol). WPA2 instead relies on AES-CCMP (Advanced Encryption System, Counter-mode CBC-MAC Protocol, whew), which incorporates the U.S. government-backed AES method that’s limited to 128 bits.

An Apple 802.11n or ac base station can offer WPA/WPA2 protection, in which both older and newer devices can join with either form of key; an 802.11b, g, or a device connects via WPA, while an n or ac device uses WPA2. Or it can offer a WPA2-only network, in which only 802.11 a and g devices that support WPA2’s advanced encryption key type can join along with all n and ac adapters.

Typically, WPA2 support, which is the default, is all that’s needed unless you have equipment that’s more than a decade old.

Note: On 802.11n networks that are set via the Radio Mode menu to use only 802.11n, WPA2 is the only available security method, because you can’t use WPA with 802.11n. On a base station that offers 802.11ac, backward compatible modes (a, b, g, and n) are always enabled, and thus WPA/WPA2 is always available to choose.

Both WPA and WPA2 come in two versions: Personal and Enterprise. The Personal versions allow the use of passphrases, long sequences of text—minimum 8 characters, maximum 63 characters—that are converted into the source material for generating an encryption key. The option to create a long phrase gives a WPA/WPA2 passphrase the potential to be memorable, but more characters in the phrase also adds entropy, the principle in cryptography of introducing a greater inability for a key to be predictable and thus obtainable by someone who doesn’t know it. A passphrase could look like my d000gs have litebritehair! I kid you not.

WPA Has a Weakness: Short Passphrases

Researchers have found that WPA and WPA2 keys are susceptible to cracking through brute force if you choose passphrases that are shorter than 20 characters and that contain only dictionary words.

To overcome this problem, choose short passphrases with a random assortment of numbers, letters, and punctuation, or create longer passphrases with a few punctuation marks, as in the example passphrase just above.

The Enterprise flavor of WPA and WPA2 requires a server to manage accounts, but simplifies access by letting people enter a username and password.

Turn On WPA/WPA2 or WPA2 Personal

Here’s how to enable WPA/WPA2 or WPA2 only:

In AirPort Utility (Mac or iOS), select and edit your base station, and then:

On a Mac: Click the Wireless button. From the Wireless Security pop-up menu choose WPA/WPA2 Personal or WPA2 Personal.

In iOS: Tap Network. Tap Security. Select WPA/WPA2 Personal or WPA2 Personal.

Enter a key of 8 to 63 characters in the password and verify fields.

On a Mac, click Update. Or in iOS, tap Done and Done again.

Wait for the base station to reboot.

The next time someone tries to connect to the network, they’ll have to enter a password to gain access; for details on entering a password, see Connect Your Devices, earlier.

Note: Macs with the original AirPort Card (models from 2003 and earlier) cannot connect to WPA2 Personal-configured networks. Yes, I’ve said this before, but I’ll keep saying it! Because it’s utterly confusing: Your older Mac with an AirPort Card won’t provide any feedback when it can’t connect to the network.

Turn On WPA/WPA2 or WPA2 Enterprise

If you or a network administrator has set up support for the enterprise flavor of WPA/WPA2, you can turn it on in Apple base stations. The enterprise flavor relies on a RADIUS (Remote Authentication Dial-In User Service) server, which handles user authentication and access. It’s where user account information and a corresponding password hash are stored, and it is used widely on business networks to allow a single sign-on for all kinds of services, including networking.

Here’s how to enable WPA/WPA2 Enterprise or the WPA2-only form:

In AirPort Utility (Mac or iOS), select and edit your base station.

On a Mac, select the Wireless view. Or in iOS, tap Network.

From the Wireless Security pop-up menu (Mac) or Security item (iOS), choose WPA/WPA2 Enterprise or WPA2 Enterprise.

Set up your RADIUS information.

On a Mac: If the dialog for configuring RADIUS doesn’t appear automatically, click the Configure RADIUS button.

In iOS: Tap Network to return to the Network screen, which now has RADIUS-related fields.

Enter the information for your server in the provided fields.

On a Mac, click Save and Update. Or in iOS, or tap Done and Done.

After the base station has restarted, you can connect from most operating systems using a valid name and password registered in the back-end server’s database.

Set Up Guest Networking

If you want to preserve the security of your network while still allowing visitors and others to access it, you can take advantage of a feature available to any simultaneous dual-band base station: Guest Network. This exceedingly nifty feature splits your Wi-Fi network into two separate networks (technically creating two virtual LANs) while using all the same actual hardware.

The guest network provides users with Internet access, but doesn’t pass any traffic to or from the main network. People connecting to a guest network can’t access computers or devices on your main network, including printers.

Another advantage of a guest network is that it can have a different password from your main network password, which you may not want to share with guests, especially if you use that password in other places too. Or, if you don’t password-protect your guest network, guests can gain wireless Internet access with no hassle, and you’ve not put other network resources at risk.

A guest network always uses both bands, and it always has the same network name on both bands. There’s no option to change either behavior. You also can’t throttle a guest’s access if she’s using excessive bandwidth or most of your Internet connection.

To set up a guest network, follow these steps:

In AirPort Utility (Mac or iOS), select and edit your base station.

On a Mac, click the Wireless button (Figure 139). Or in iOS, tap Guest Network.

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Figure 139: The Wireless view lets you set options for visitors to use your Internet connection without accessing your main network.

Now:

On a Mac: Select Enable Guest Network and name the network. Optionally, set a password: choose WPA2 Personal or WPA/WPA2 Personal from the Guest Network Security pop-up menu, enter a password, and then re-enter it to verify it. Click Update.

In iOS: Turn on the Guest Network switch, and then tap Guest Network to name the network. If you like, set a password: tap Security, tap WPA/WPA2 Personal or WPA2 Personal, and then tap Back to return to the Guest Network screen; then, fill in and verify the password. Tap Done, and then tap Done again.

The name of the new guest network appears in the Wi-Fi menu on any nearby Mac, and in the Wi-Fi listing on any other nearby device.

To enable guest roaming, set the name, security method, and passphrase identically on all the base stations in a network.

Overcome Interference

A frustrating part of Wi-Fi networking is that you can’t control your “air space.” All too often, neighboring Wi-Fi networks and other emitters cause reception problems in areas that otherwise would have good reception. If your network’s performance varies by time of day or even by the minute, the ideas in this chapter may help you identify the problem.

Do Some Basic Testing

What you test for varies by band. Keep reading after the tests for some suggestions for how to fix found problems.

For 2.4 or 5 GHz:

Run WiFi Explorer to determine whether other networks are running nearby. It scans for networks and can display their characteristics, such as signal strength and whether security is enabled. It can’t tell you more general info about signals being generated in the spectrum range, however. (See Measure with WiFi Explorer.)

For 2.4 GHz only:

Investigate your cordless phones and microwave oven as culprits—they can both create static on the Wi-Fi line. Do you have problems only when talking on the phone or making popcorn? There you go.

Is your Wi-Fi network near a hospital, or light or heavy industry? Some medical and industrial devices use the 2.4 GHz band, including microwave sealers that close bags of potato chips. You might need to use wired Ethernet or upgrade to computers that can use the 5 GHz band to overcome that problem.

For 5 GHz:

Check whether you have 5.8 GHz cordless phones.

See whether a wireless ISP might be broadcasting over 5 GHz in your area. Most wISPs are using the 5.8 GHz section of the 5 GHz band. (If that’s the case note the second bullet item in the solutions for cordless phones, below.)

Try a Solution

Here are ideas for solving some of the problems noted just previously.

If cordless phones are the culprit:

Buy new cordless phones that use a band that doesn’t interfere with your Wi-Fi network. The popular DECT standard finally entered the United States a few years ago in its DECT6 version, which relies on 1.9 GHz signals. You can also find 5.8 GHz cordless phones.

In 5 GHz, use lower-numbered channels; 5.8 GHz falls within the highest range of channels supported by 802.11n base stations. (This solution also reduces interference from any wireless ISPs, firms that provide residential Internet service in 5GHz.) Using a lower-numbered channel will reduce the signal strength of your network by 95 percent, but it might be the only solution in extreme cases.

If a neighboring network is causing the problem:

If you know your neighbors, you could make an informal agreement to reconfigure your networks to use static channels that don’t overlap as much as possible instead of using automatic channel assignment. In 2.4 GHz, you might split up 1, 6, and 11; in 5 GHz, you could discuss using different channels or lower-powered channels

You (and your neighbors) could move your access points farther away from one another to reduce the signal conflict in the middle.

If you can’t communicate with your neighbors, you can unilaterally make changes:

For 2.4 GHz channels, pick a fixed channel that’s least used by neighbors.

For 5 GHz channels, turn up the “volume” by picking channels numbered 149 and above, which use up to 20 times the signal power of lower-numbered channels. This won’t drown out neighbors, because the 5 GHz band is very well behaved, but it will make it more likely that you receive higher throughput.

Upgrade some or all of your gear. Newer Wi-Fi hardware is better at dealing with other nearby signals.

Appendix A: Configuration Files

You can export the current state of your base station’s configuration to a file that can be imported later, to the same base station or to a different one. This is useful when you want to create a model configuration with the same network name, password, and other details, and then use it to configure many base stations.

Warning! Before importing a configuration, you should save a copy of your current active setup using the steps given just previously. Importing overwrites your current active base station settings.

To export a configuration:

In AirPort Utility for Mac, select the base station and click Edit.

Choose File > Export Configuration File.

Name the file descriptively, as there will be few other clues that help you identify the file (Figure 140).

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Figure 140: When exporting a configuration file, name it descriptively and encrypt its passwords.

Select the Encrypt Passwords for More Security box so that the file doesn’t contain your Wi-Fi, base station, or disk passwords in the clear.

Click Save.

If you want to restore a base station to the settings in a file or configure a different base station in the same way, follow these steps to import the exported configuration file:

In AirPort Utility for Mac, select the base station and click Edit.

Choose File > Import Configuration File.

Select the configuration file, and click Open.

AirPort Utility asks which settings in the configuration file you’d like to import (Figure 141). If a type of setting isn’t configured, no checkbox shows for that item, logically enough. Base stations allow timed settings, which can restrict access to given computers at given times of the day or week; port mapping rules for allowing inbound access to local computers; DHCP reservations for assigning addresses to local computers; and miscellaneous other settings.

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Figure 141: Select settings to import.

Select the options you want to import, and click OK.

Enter a password if prompted.

Click Update to apply the imported profile’s settings.

Once the file is imported, the settings replace your current base station settings.

Tip: Importing just items like Timed Access Control or DHCP Reservations lets you transfer just those settings among multiple base stations after you update them on one base station without resetting the other base stations’ names or assigned IP addresses.

Appendix B: Setting up a Software Base Station

You can use a Mac equipped with a Wi-Fi adapter card not just as a client on a Wi-Fi network, but also as a base station. In this appendix, I explain how to set up a software base station in 10.5 Leopard and later, as well as how to use Ad Hoc Networking, which has some elements in common with software base stations.

Software Base Station or Ad Hoc Network?

A software base station walks and talks like a base station: it puts out the same kind of messages that other computers recognize from a base station. You need at least two network interfaces to turn on a software base station: a Wi-Fi adapter plus some other interface, like an Ethernet network connection.

Ad hoc networking is a computer-to-computer mode, and it doesn’t require a second adapter to reach another network, although it can handle that. Ad hoc can be used sometimes by simpler devices. I highly recommend avoiding ad hoc networking: an ad hoc network can’t use modern WPA2 security because that method requires a central hub to manage the encryption process.

Most operating systems distinguish between ad hoc networks (which are sometimes seen as more risky) and base stations. The fact that you can create software base stations eliminates the risk distinction; crackers use software-base-station programs to lure hotspot users, for instance.

Software Base Station

The software base station is a breeze to set up: pick a channel, set security (which I recommend), and turn it on. Let me explain your tradeoffs for channel choices and security first, however.

Frequency

10.7 Lion was the first release of Mac OS X that allows you to select either a 2.4 GHz or 5 GHz channel for use with a software base station. You can pick any 2.4 GHz channel, as well as 5 GHz channels 36, 40, 44, and 48. (These channels vary by country.) Apple is offering only 4 of the 8 channels available in its dedicated base stations, which are just 8 of the 23 legal channels in the United States.

These lower-numbered channels (36, 40, 44, and 48) broadcast at no more than 5 percent of the maximum legal power of the higher-numbered channels according to U.S. rules. Apple must have thought it better to use lower power and thus not interfere with any nearby networks (read Channels for more ).

Security

After years of providing lackluster security for the software base station, Apple finally upgraded it in 10.8 Mountain Lion (and didn’t advertise the fact). Mountain Lion added WPA2 Personal security, which provides the highest degree of security available. WPA2 Personal replaced the older WEP encryption, which I described back in Use Built-in Encryption, in 2004. Yosemite eliminated WEP as a hidden option.

In Mountain Lion and later, as you follow the steps ahead for turning on a software base station, you’ll be able to choose None or WPA2 Personal as the security method. None will let anyone join, of course, while WPA2 Personal requires that other devices have the passphrase you set. Nearly every piece of hardware labeled “Wi-Fi” shipped since 2004 (and some from 2003) can work with WPA2 Personal security.

Starting up Software Base Station

The Software Base Station feature is found in the Sharing preference pane. Before starting, make sure you have another connection active in the Network system preference pane—such as Ethernet or even machine-to-machine FireWire—because you can’t create a software access point without another active network connection.

For this example, I assume your Internet connection comes via Ethernet from a cable modem. Here’s what to do:

Go to System Preferences > Sharing, and select the Internet Sharing service (Figure 142).

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Figure 142: With Internet Sharing highlighted, you can share your wired Internet connection as a software base station by choosing, for example, Ethernet and checking Wi-Fi. (The checkbox for Internet Sharing isn’t enabled until you click the box in Step 6.)

From the Share Your Connection From pop-up menu, choose Ethernet (Figure 143). (The menu item for Ethernet may vary; due to the adapters on my system, I have several Ethernet options, not all of which are always available. On most Macs, you’ll see just Ethernet.)

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Figure 143: The Share Your Connection From pop-up menu lists all active network connections.

Select the Wi-Fi checkbox in the “To computers using” list. (This also works with any other active Internet connection, so long as it’s not Wi-Fi!)

If you want to also share a connection via other active interfaces to other devices connected via your Mac, check any of the additional boxes in the “To computers using” list. For instance, you might have a device connected via a Bluetooth PAN (Personal Area Network) that could be fed Internet access from your Ethernet connection.

Click Wi-Fi Options to set the network name, channel, and, if you like, a WPA2 Personal passphrase by choosing WPA2 Personal from the Security pop-up menu (Figure 144). Click OK. (The start of this section has advice on channel and security options.)

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Figure 144: Set the wireless options you want for your software base station, including a WPA2 Personal passphrase.

Check the Internet Sharing box to start the service.

An alert asks you to confirm that you want to turn on Internet Sharing; click Start.

If it starts successfully, a green dot appears to the left of “Internet Sharing” above the Share Your Connection From pop-up menu, and the word Off changes to On.

Ad Hoc Networking

Ad hoc networks have no center: every computer that joins or advertises an ad hoc network is just as important as every other. If you network a group of machines together informally, with some coming and going now and again, ad hoc networking will work, whereas a software base station would fail if the central party was a laptop that left the network. For instance, you might create an ad hoc network to use Bonjour for transferring files among the computers.

When you first set up an ad hoc network, your Mac assigns itself an IP address in the 169.254.x.x range, where x is a number between 1 and 254; Macs that connect to your network pick up addresses in that range so that they can communicate. Bonjour services in iChat should work fine over ad hoc networks.

Warning! Apple removed all security options from ad-hoc networks, making it a real gamble to use, as anyone in the vicinity can connect. Choose to use a software base station instead.

To set up ad hoc networking, follow these steps:

From the Wi-Fi menu, choose Create Network.

Enter a network name and choose a channel (Figure 145). See Channels if you need help with picking a channel.

[picture]

Figure 145: Create an ad hoc network by filling in these settings.

Click Create to create the network.

Your Wi-Fi menu now shows a computer-in-a-fan icon, which indicates that ad hoc networking is in use.

To turn off an ad hoc network, open the Wi-Fi menu and choose Disconnect from your network name. You’ll find the command under a Devices label, in the menu below the names of any regular Wi-Fi networks in the vicinity (Figure 146).

[picture]

Figure 146: The Devices section of the Wi-Fi menu lets you turn off an ad hoc network by choosing Disconnect.

Appendix C: Channels Explained

The ins and outs of the channels used in each band have wound up in this appendix, as you may need to know the details only when something goes wrong—or you may simply want to know more about the technical minutiae of Wi-Fi. In this appendix, you can learn why the 2.4 and 5 GHz channels are organized the way they are, and what happened to 15 missing 5 GHz channels.

Channels in 2.4 and 5 GHz are 20 MHz wide; an optional 40 MHz wide, or double-channel, option was added in 802.11n, although Apple allows 40 MHz wide channels only in 5 GHz. 802.11ac expanded this to offer quadruple-wide 80 MHz channels (wave 1) and octuple-wide 160 MHz channels (wave 2). The two bands have different ways of defining and making those channels available.

Channel availability varies from country to country. Apple lists which channels it supports in the technical specs for its base stations. You can also see a table of 5 GHz channels worldwide in Wikipedia.

MHz and Mbps

Megahertz does, in fact, correlate to megabits per second. Shannon’s Law (or the Shannon-Hartley Theorem), a bit of information theory, says that there’s a direct relationship that ties the width of a channel and the ratio of signal to noise to the achievable data rate. Twice the channel width means up to twice the raw data (Figure 147).

[picture]

Figure 147: Shannon’s Law (image via Wikipedia).

In case you were wondering, the formula is: maximum bit rate equals channel width in hertz multiplied by log2 of the sum of 1 + signal divided by noise.

See Pick Compatibility and Set a Channel, earlier, to learn how to set your base station’s channel in AirPort Utility.

2.4 GHz Channels

In the United States, 802.11 standards can use any of 11 numbered, staggered channels in the 2.4 GHz band (Figure 148). Because these channels are staggered and overlap, only channels 1, 6, and 11 in the United States can be used in networks that overlap their coverage area, assuming you want the least interference. (In some countries, the 2.4 GHz band is slightly wider, allowing for four non-overlapping channels.)

[picture]

Figure 148: 2.4 GHz 802.11 channels are staggered, with channels 1, 6, and 11 having the least overlap. 5 GHz 802.11 channels have little overlap; only the four lowest channels of 23 are shown.

All 2.4 GHz channels have the same power limits, but there’s a distinct difference in the permitted level of signal strength—which affects the distance at which Wi-Fi can work and the top speeds available.

Also, due to the overlapping, staggered nature of the channels, there is room in 2.4 GHz for only a single unique 40 MHz channel and a single 20 MHz channel to be used at the same time—and then only in ideal cases. This is why Apple didn’t want wide channels in 2.4 GHz.

Note: For the full detail about the limitations of wide channels in 2.4 GHz, read a long article I wrote for my Wi-Fi Networking News site about the three protection mechanisms: intolerance, clear-channel assessment, and politeness.

5 GHz Channels

The 5 GHz band can be divided into 23 channels in the United States for 802.11a, n, and ac. The regular-width channels are the same 20 MHz width as the 2.4 GHz band channels. These channels overlap only at the fringes, and thus allow many different networks to work in the same space with little interference.

Explaining Channel Numbering

Channels in 2.4 GHz and 5 GHz are numbered in units of 5 MHz, even though Wi-Fi uses 20, 40, 80, or 160 MHz channels. In 2.4 GHz, these channels are numbered sequentially from 1 to 11 because the channels overlap. 5 GHz channels jump and aren’t sequential. Why? Two reasons:

Because 802.11a/n/ac channels don’t overlap, the numbered channels increase by four (5 MHz multiplied by four) for each selectable 20 MHz regular-width channel, or by 8, 16, or 32 for 802.11n and ac channels.

There are four separate hunks of allotted unlicensed 5 GHz bandwidth. The first two (which comprise channels 36 through 64) are contiguous; we then jump to channels 100 to 136, and finish in 149 to 161. There’s a 24th channel, 165, that’s not supported in 802.11 specifications. (Another chunk of 100 GHz below channel 36 was recently approved in the United States for public use, but the necessary hardware isn’t built yet.)

The 5 GHz unlicensed band is sometimes called (for historical reasons) the UNII (Unlicensed National Information Infrastructure) band. This is divided into four pieces: UNII-1 (4 channels), UNII-2 (4 channels), UNII-2 Extended (11 channels), and UNII-3 (4 channels).

Apple’s base stations support just the UNII-1 and -3 sections, even though Apple’s client hardware can use any UNII frequencies. UNII-1 (channels 36, 40, 44, and 48) has a maximum permitted signal strength that’s 5 percent of the strength allowed in UNII-3 (149, 153, 157, and 161).

That’s right: when broadcasting over the upper band, devices may emit as much as 20 times the signal strength. In the 2009 and 2011 updates to Apple’s AirPort gear, Apple has continued to increase the power emitted by the upper 5 GHz channels, too, so that signal strength is closer to the maximum permissible amounts.

With 40 MHz channels, only channels 36, 44, 149, and 157 are available; since wide channels are really a set of two normal channels, a wide version of 36 is actually 36 plus 40, 44 is 44 plus 48, and so forth. With 80 MHz channels, it doesn’t matter which base channel in either group of four you choose; the base station will always try to use the other three channels if no other networks are sensed on them while it tries to use them. If there are active networks, 802.11n and ac backs down to as little as 20 MHz (using the base channel selected) until no other traffic is sensed. For 802.11ac wave 2, 160 MHz of contiguous space will be nearly impossible, so base stations equipped for that width will be able to use an “80+80” configuration: two separate bandwidth swaths, each 80 MHz wide.

When any Apple 802.11n or ac base station is set to choose a channel automatically, it tries to pick an upper-band channel in 5 GHz in order to broadcast with a greater signal strength. Interference will drive it to a lower channel, so it may be worth setting the channel manually for the extra distance, even if interference is an issue.

The Missing 15 Channels in UNII-2 and UNII-2 Extended

It’s no mystery where the UNII-2 and -2 extended channels went. These bands overlap with some American military radar use. A compromise among industry, regulators, and the military opened up 11 new channels (the -2 extended section), but also imposed new rules on the existing 4 channels in UNII-2.

To use these 15 channels, chipmakers and manufacturers must put procedures in place to avoid interfering with some military and weather-sensing radar, despite these uses of radar being high-power, used at limited times, and restricted to relatively small parts of the United States. A device must sense radar patterns and stop using a channel for 10 minutes when it detects a radar pattern, and it must also automatically use the least amount of power necessary. (These requirements were bundled in 802.11h, a standard developed to meet European requirements, and they are also used in the United States in the affected channels.)

False positives for detecting radar are frequent, and thus equipment makers like Apple choose to not offer them, in order to avoid frustration and dropped network signals. Change may be afoot to make these rules more sensible, at which point firmware updates could make them available.

The -2 and -2 extended bands can use about five times as much power as the UNII-1 band and one-quarter as much as the UNII-3 band.

Appendix D: What and Where Is a MAC Address?

The MAC, or Media Access Control, address is a unique, factory-assigned address for every Ethernet and Wi-Fi adapter. A MAC address consists of six two-digit hexadecimal numbers separated by colons, such as 0C:F2:33:01:02:FC. (Hexadecimal, or hex, is the base 16 number system, with values running from 0 to 9, and then from A to F for 10 to 15.) The first three numbers are assigned to a manufacturer by a coordinating association; Apple has at least two common ranges, which begin with 00:0a:95 and 00:03:93. MAC addresses are often used for filtering, authentication, and WDS, often without requiring direct entry.

Some routers from other makers can have their MAC address changed in a process called MAC cloning or spoofing, which is sometimes useful when you have to register a computer’s MAC address, but then want to use a router in its place. No Apple base station has ever offered this capability, although Mac OS X allows it for Macintoshes via a Terminal command.

Here are various ways to locate Mac addresses.

From a Base Station

For a base station that pre-dates the 2013 802.11ac models, look on the bottom of the unit:

The AirPort ID or Wi-Fi ID is the wireless MAC address. From 2009 to 2012, all models of the Extreme and Time Capsule as well as the 2012 Express have two AirPort IDs, one for each band’s radio, and they are noted by band on the base station.

The Ethernet ID is the WAN port’s MAC address.

Or in AirPort Utility for Mac, select a base station and hover over the network’s name to see a popover containing the MAC addresses, as in Figure 149.

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Figure 149: View the base station’s MAC addresses by hovering over the name.

Even better, in AirPort Utility for Mac, Option-double-click the base station icon or Option-click the Edit button (Figure 150). Now, you can select and copy a MAC address, which you can’t in the popover, plus you can view all the wireless clients’ MAC addresses at once in the scrolling Wireless Clients list.

[picture]

Figure 150: The Summary view lets you copy MAC addresses.

Or in AirPort Utility for iOS, select the base station icon and then tap Hardware Info.

From AirPort Utility for Mac

In AirPort Utility for Mac, select the base station and hover over a connected device’s name in the Wireless Clients list (Figure 151).

[picture]

Figure 151: Wireless Clients reveal information about connected devices when you hover over a name in the list.

The Name shows either the value entered in the Network system preference pane on the Mac or a Bonjour name.

In a Mac’s System Preferences

On a Mac, go to System Preferences > Network. Click Wi-Fi in the adapter list, and click the Advanced button. The MAC number is described as the Wi-Fi Address at the bottom of the Wi-Fi view.

In Windows 10

Windows 10 does a fine job of deeply burying the MAC address. Laptop mag has a nice article with instructions accessing the Mac address from the Command Prompt or Control Panel.

In Android

Go to Settings > Wi-Fi, tap the three-vertical-dot button, and select Advanced. The MAC Address appears in that view; you may need to swipe to find it.

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About the Author

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Glenn Fleishman is a veteran technology and science reporter. He’s an editor at large at the Wirecutter, an independent editorial site that researches and reviews products, and a senior contributor at Macworld, where he writes the weekly Private I and Mac 911 columns, hosts its podcast, and regularly pens reviews and features.

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Take Control of Your Apple Wi-Fi Network
ISBN: 978-1-61542-438-2
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