Take Control of Your 802.11n AirPort Extreme Network (1.2)

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Take Control
Your 802.11n AirPort
Extreme Network
Glenn Fleishman
Table of Contents (1.2)
Read Me First ...................................................... 2
Introduction ........................................................ 5
AirPort Networking Quick Start .............................. 6
Quick Troubleshooting Guide ................................. 8
Key Glossary Terms ........................................... 10
Learn Wireless and AirPort Basics......................... 13
Put Your Base Station into Action ......................... 25
Set Up Your Network .......................................... 54
Connect Your Computers .................................... 70
Connect Multiple Base Stations ............................ 86
Mix Legacy, New N Networks............................... 97
Reach Your Network Remotely........................... 101
Set Up a Shared USB Printer ............................. 113
Set Up a Shared USB Disk................................. 121
Secure Your Network........................................ 132
Overcome Interference ..................................... 146
Appendix A: Stream Media with AirPort............... 150
Appendix B: Setting up a Software Base Station .. 158
Appendix C: Advanced Extreme Features ............ 161
Appendix D: What’s New in Leopard ................... 167
About This Book............................................... 179
Welcome to Take Control of Your 802.11n AirPort Extreme Network,
version 1.2. This book helps you install and get the most out of an
802.11n Wi-Fi network. This book was written by Glenn Fleishman,
edited by Tonya Engst, and published by TidBITS Publishing Inc.
Copyright © 2008 Glenn Fleishman. All rights reserved.
The price of this ebook is $10. If you want to share it with a friend,
please do so as you would a physical book. Click here to give your
friend a discount coupon. Discounted classroom copies are also
You may not have the latest version of this PDF. To find out if there’s
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Who Needs This Book
I wrote this book for people who have purchased or are considering
buying the thoroughly overhauled, 802.11n AirPort Extreme Base
Station, released in January 2007 with new software, and updated
with new hardware and revised software in August 2007. My goal is
to help you configure this base station model to meet your needs, and
to use it with existing and new networking equipment and computers.
Who Doesn’t Need This Book
If you’re not yet using a 2007-or-later, 802.11n AirPort Extreme Base
Station, this book would be worthwhile only for background research
if you are considering buying that new base station. If you use earlier
networking hardware on a Mac, consider purchasing Take Control
of Your AirPort Network, which covers gear released before 2007.
In reading this book, you may get stuck if you don’t know certain
basic facts about Mac OS X or if you don’t understand Take Control
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syntax for things like working with menus or finding items in the
Finder. Please note the following:
• Path syntax: I occasionally use a path to show the location of a
file or folder in your file system. Path text is formatted in bold type.
For example, the Airport Utility gets installed into the Utility folder,
which is located inside the Applications folder. The path to AirPort
Utility is: /Applications/Utilities/AirPort Utility.
• Menus: When I describe choosing a command from a menu in
the menu bar, I use an abbreviated description. For example, the
abbreviated description for the menu command that creates a new
folder in the Mac OS X Finder is “File > New Folder.”
• Finding preference panes: I sometimes refer to Mac OS X
preferences that you may want to adjust, such as the Network
preference pane. To reach this pane, open System Preferences
by clicking its icon in the Dock or choosing System Preferences
from the  menu. You access a particular preference pane by way
of its icon, or the View menu. For example, to see “the Network
preference pane,” you would launch System Preferences and
then click the Network icon or choose View > Network. To see
“the AirPort view of the Network preference pane,” you would
do the same thing, and then click AirPort.
• Configuring a base station: Throughout the book, I refer to
using a program called AirPort Utility to configure a base station.
To configure a base station in almost all cases, you launch or
switch to AirPort Utility, select the base station in a left-hand list
of base stations, and then choose Base Station > Manual Setup
(Command-L) to proceed.
What’s New in Version 1.2
Leopard shipped several weeks after the 1.1 version of this book, and
there was nothing to be done but wait to see what shook out—and boy
did a lot shake out, including Apple’s release of Time Capsule, an
updated AirPort Express, and another overhaul of their AirPort
Utility. As a result, this updated version 1.2 features an extensive
appendix documenting changes in Leopard. An upcoming new book,
tentatively titled Take Control of Your Draft N AirPort Network in
Leopard, will thoroughly address all the new backup and network
options separately.
Page 3
See Appendix D: What’s New in Leopard (p. 167) for the rundown
on how the Network preference pane changed, how the new AirPort
menu works, and how to configure a host of small tweaks that have
moved since Tiger.
Also, in areas of the book where the new appendix has important
information about Leopard, I’ve added a leopard spot ( ) in the
margin. If you see the spot, you can click it to view the appendix. If
you find yourself moving around a lot due to clicking the spots, you
may find it handy to use a keyboard shortcut to quickly return to the
previous location. Look in the menus to find the shortcut for your
PDF software.
What Was New in Version 1.1
At first, this revision was intended to be a 1.0.1 update, to cover the
changes in the AirPort Extreme Base Station with 802.11n that Apple
introduced in August 2007. After reviewing reader mail and spending
many hours working with the gigabit model, I wound up making a
number of changes and additions that should help with setting up
regular networks and those with multiple base stations.
In this update, I added the following:
• An updated discussion of the state of 802.11n. See Extreme N
Details (p. 18).
• More information about Third-party adapters for 802.11n (p. 22).
• A new section, Connect Multiple Base Stations (p. 86), which
explains in detail how to use Ethernet and Wi-Fi links to build
a network of two or more base stations to cover a greater area
or increase the speed of the network.
• For mixed networks using older 802.11 standards with 802.11n,
I recommend that you attach USB printers to an Extreme N Base
Station. See Put Printers in the Right Place (p. 99).
• Updated information about NAT-PMP and wide-area Bonjour,
Apple technologies for extending access to local network resources.
• To the section on coping with interference, I added more specific
advice. See Eliminate Conflicting Signals (p. 146).
Page 4
Apple introduced integrated wireless networking to the world with
AirPort in 1999. Although corporations had already been using forms
of wireless networking for warehouse tracking and to connect buildings in a large campus, the cost was high, speeds were low, and complexity was manifest. Other companies were selling similar wireless
hardware in 1999, but Apple’s products shot off the shelves due to
their relatively low initial price, simple configuration interface, and
excellent performance.
AirPort came out of the same approach that allowed Apple to ship
the iMac the year before: combining available, standard parts in a
unique package that provided more value as a whole.
The AirPort Card fit into a special slot in Macintoshes; its standalone, central coordinating hub was called the AirPort Base Station.
Apple replaced the original AirPort line with AirPort Extreme: first,
in 2003 with a somewhat faster flavor (known as 802.11g), then again
in 2007, with a substantially faster version (802.11n). Today, AirPort
Extreme is built into every Mac, except the Mac Pro, for which it is an
add-on option, and the Xserve, which is designed for server rooms.
Despite Apple’s 8-year history with wireless networking and the
general excellence of their software and support, setting up a wireless
network isn’t always a snap. This book helps you set up a wireless
network and offers tips to help save time, improve security, extend
range, and enjoy a technical edge when working with AirPort.
Although the title of this book references 802.11n AirPort Extreme
networks, I also cover compatibility and connections with older
hardware, as well as connecting to a new network using Mac OS X,
Windows XP, and Windows Vista.
I start with wireless basics, move through installation and configuration, explain how to share printers and hard disks, tell you how
to connect to a Wi-Fi network, give advice on extending a network’s
range and quality, look at adding devices like an Apple TV or AirPort
Express, and finish with how-to information on security for those who
want their AirPort networks safe from freeloaders and intruders.
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If you read this book in order, you’ll be guided through the steps
shown below—unpacking an 802.11n AirPort Extreme Base Station,
configuring the gateway, and getting on the Internet. The book also
guides you through adding devices like printers, hard disks, and
Apple TV, and securing the network.
Need a quick solution? If you are reading this book in order
to solve a particular problem, flip ahead two pages to the Quick
Troubleshooting Guide, also, you may especially wish to consult
Eliminate Conflicting Signals (p. 146).
Learn wireless basics:
• Get a quick grounding in wireless terminology and technology.
See Key Glossary Terms (p. 10) and Learn Wireless and AirPort
Basics (p. 13).
Set up your network:
• Unpack and power your base station (p. 25), and Install new
software (p. 27).
• Handle initial setup (p. 32) for the base station. This might be all
you need to get on the Internet.
• Learn about options and tradeoffs for which frequency band and
channel to use, in Configure the Spectrum and Channel (p. 47).
• Place your gateway in the right place for optimum coverage. See
Pick the Right Place for Your Base Station (p. 49).
• Hook your AirPort Extreme into the Internet or a larger network,
while learning the difference between public and private network
addresses, and static and dynamic addresses in Get a WAN
Address (p. 55).
• Set up your local network connections for computers to connect
wirelessly and via Ethernet to the base station. Read Hand Out
LAN Addresses (p. 61).
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• Control how your computers connect to the network with Connect
Your Computers (p. 70), which covers Mac OS X, Windows XP
Service Pack 2, and Windows Vista.
• Open your local network up to the wider world in limited ways
for gaming, remote control, and Web servers. See Reach Your
Network Remotely (p. 101).
• Add printers and external drives to your base station to share
across the network—or the Internet. See Set Up a Shared USB
Printer (p. 113) and Set Up a Shared USB Disk (p. 121).
• Stream media on your network through an Apple TV (p. 150) or
with AirPort Express and AirTunes (p. 154).
Extend your network with more routers:
• Add access points to your network with the right settings to create
seamless roaming. See Connect Multiple Base Stations (p. 86).
• Don’t throw away your old gear: combine old and new for the best
of both worlds. See Mix Legacy, New N Networks (p. 97).
• Extend your network over your home electrical system. Read the
sidebar Extend with HomePlug (p. 90).
• Bridge Wirelessly among access points, in order to avoid wiring
(p. 91).
Secure your network:
• Decide if you need encryption. Read Likelihood, Liability, and Lost
Opportunity (p. 132).
• Avoid security tricks that don’t work, while using a new method
that does. See Simple Tricks That Don’t Work (p. 134).
• Apply encryption using the best—and often simplest—method.
See Use Built-In Encryption (p. 137).
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If you need quick help, here’s the starting point.
Reset the Base Station from a Lock-Up
If your AirPort Extreme Base Station can’t be seen over the network
via AirPort Utility (see Install new software, p. 27), and you cannot
connect to the base station or the Internet via a Wi-Fi-enabled
computer, try these steps in order:
1. Check 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 one of the
base station’s LAN ports. Try AirPort Utility again.
2. Failing a direct Ethernet connection, try power cycling:
Pull the power adapter’s plug out of the wall socket or remove the
end that plugs into the base station. Wait 10 seconds. Plug it back
in, and try to connect via AirPort Utility. Everything may be back
to normal.
3. Failing power cycling, try a factory reset: This step erases
any the custom settings you’ve made (I recommend backing up
settings using AirPort Utility; see Create and manage profiles,
p. 38). To reset the base station, straighten one end of a paperclip,
and with the base station plugged into power, hold down the base
station’s reset button with the paperclip end. The reset button is
recessed in the rear right of the base station below the reset
symbol: a white arrow reversed out of a gray circle.
4. Failing power cycling, try to reset another way: Unplug
the base station from power, push in the reset button and hold it
down, plug the base station into power, and keep the reset button
pressed for at least 20 seconds.
5. Failing factory reset: Call Apple for return instructions.
Page 8
Printer Problems
Printer on 802.11g part of network won’t print
You’ll need to connect it to your Extreme N base station. Put Printers
in the Right Place explains how (p. 99).
Can’t print to a USB-connected printer
See Troubleshoot an Unavailable Shared USB Printer (p. 120).
Other Troubleshooting
Can’t see base station’s network from all computers
Did you set the base station to the 5 gigahertz (GHz) band? Only
newer Macs with 802.11n built in can connect. See Configure the
Spectrum and Channel (p. 42).
Can’t connect to base station’s network; get an error instead
If you can see its network name, try these fixes:
• Did you inadvertently set the base station to allow 802.11n only
connections in the 2.4 GHz band? See Connect Your Computers
(first Warning, page 70). It’s also possible that access control is
preventing access. See Mac address filtering (p. 135).
• It’s possible that interference in your area from other networks is
preventing you from connecting. You may need to change the base
station’s channel. See Eliminate Conflicting Signals (p. 146).
Error occurs after connecting to the base
station with the correct encryption key
Are you using a Mac with the older AirPort Card with your base
station set up with WPA2 encryption? See Turning on WPA/WPA2
with AirPort Extreme (p. 141).
Firmware update makes base station act erratically
Try to Revert to Older Firmware (p. 161).
Network works erratically
Another network might be interfering with yours. See Eliminate
Conflicting Signals (p. 146).
Conflicting signals seem to cause network problems
See Eliminate Conflicting Signals (p. 146).
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In this section, I’ve defined a few terms that you’ll encounter over
and over in this book. Read the list below to become familiar with any
new terms and refresh your memory on the rest. I also define these
terms where they occur. I’ve presented the concepts below in the
order you need to understand them, building one on top of the other.
Wi-Fi: The set of wireless networking standards that encompasses
all of Apple’s AirPort products, and thousands of wireless networking
products made by other firms. The in-progress 802.11n standard used
in the latest AirPort Extreme Base Station is slated to become part of
Wi-Fi in third quarter 2007.
Ethernet: A set of standards for connecting computers by wire,
typically at speeds of 10 megabits per second (Mbps), 100 Mbps,
and 1,000 Mbps. 1,000 Mbps Ethernet is commonly called gigabit
Local Area Network (LAN): A LAN comprises computers
connected via Ethernet and/or Wi-Fi into a small or large group.
A LAN’s computers are in close physical proximity, usually in an
area as small as a home office or as large as an entire office building.
A LAN is typically thought of as a single network, especially when
considering local network resources like fileservers.
Wide Area Network (WAN): A router, like the AirPort Extreme
Base Station, connects its own LAN to a wider network that’s known
as a WAN. A WAN, from the perspective of a base station, is often
simply the Internet; or it might be a network connecting several
offices run by the same company in different cities.
Access point: A wireless networking device that accepts connections
from clients or other access points in order to move network traffic
over the air.
Base station, router, gateway: These three terms are used
somewhat interchangeably to refer to the central Wi-Fi hub that
connects a LAN to a WAN. Routers, often called gateways, connect
different kinds of networks and allow devices on each network
to communicate with each other. Apple calls its combination of an
access point and gateway a base station; other companies call these
Wi-Fi gateways or Wi-Fi routers.
Page 10
MAC (Media Access Control) address: The MAC address is a
unique number assigned by a manufacturer to each network adapter,
including Ethernet adapters and Wi-Fi adapters. The MAC address
is used to identify an adapter on a LAN. (Media here is the plural
of medium, as in the access medium: the physical means over which
data flows.) To learn how to find a device’s MAC address, see the
sidebar What and Where is a MAC Address? (p. 59).
Larger LAN: A base station often creates a LAN for computers
connected to it. But in larger networks, the base station is connected
via its WAN port to a “larger LAN”—despite the name of the port, this
is a local network, but it typically has services that are passed through
to the base station-connected computers. The larger LAN handles
functions that an Internet service provider (ISP) would.
Often, the settings for an Apple base station are different when you
connect it to a broadband modem and the Internet—a simple WAN
connection—than when you connect the base station to a larger LAN.
Internet Protocol (IP) address: An IP address is a number
assigned to a network interface, like an Ethernet card or a Wi-Fi
radio, that allows it to be identified uniquely on a local network or
the Internet. A device needs an IP address in order to interact with
Internet services such as an email server or a Web site.
Private IP addresses: Private IP addresses, also called simply
private addresses, are assigned in LANs from a pool of globally
reserved IP address prefixes. Private addresses are not reachable
or routable from outside the LAN without extra work: Internetconnected computers can’t directly address private IP addresses,
and require an intermediary to help (see Network Address
Translation, below).
Public IP addresses: Public IP addresses, also frequently called
public addresses, are drawn from the global pool of IP addresses that
can be routed, or reached, from any other computer on the Internet.
These are colloquially called real IPs. (Public addresses access can
be restricted through firewalls, however.)
Network Address Translation (NAT): NAT provides a workaround that lets computers outside a LAN reach privately addressed
computers inside a LAN. NAT maps outgoing connections from
computers within the LAN to an address on the WAN side of a router,
Page 11
allowing a response to that outgoing connection, like a Web page
being requested and retrieved. NAT can also map in the other direction. I discuss how this mapping can be safely controlled in Map Ports
for Remote Access. A NAT gateway is not a firewall, although it’s
often marketed as one.
Dynamic Host Configuration Protocol (DHCP): DHCP is
used to assign IP addresses to computers and other equipment on a
network. Any device that can connect to a network has a DHCP client
built in, and that client can request and retrieve an address from the
network gateway.
The AirPort base station has a DHCP server to provide this function.
The base station also has a DHCP client that operates on its WAN
port to request an address—if necessary—from the higher-level
network to which it is connected.
In some cases, the DHCP server in the base station is redundant
and needs to be turned off to avoid interfering with other elements
of a network. In other cases, you might disable a computer’s DHCP
client so that you could enter a fixed IP address. DHCP and NAT
are often used together: NAT allows a private address to reach the
Internet; DHCP assigns that private address to a computer or other
networked device.
Page 12
Let’s quickly run through some wireless basics to set the stage for
what follows.
Access Points and Adapters
AirPort and Wi-Fi networks need two connected parts: a wireless
adapter and an access point. The wireless adapter is part of a computer or mobile device, while the access point, in many ways, works
just like an Ethernet switch. An access point that’s coupled with
a router is called a wireless gateway; Apple’s wireless gateway is
called a base station.
NOTE You might have heard of AirPort Extreme by the name Wi-Fi, which
is a certification guarantee for which The Wi-Fi Alliance trade group
owns the rights and controls the testing. Wi-Fi loosely connotes
wireless fidelity, in the sense of faithfulness: devices with Wi-Fi
stamped on them work with other Wi-Fi devices, or are faithful to
one another.
NOTE 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
XP or Vista—or in conjunction with other AirPort equipment.
Examples of such features include streaming audio, hard-drive
sharing, and base-station-to-base-station connections.
The wireless adapter uses client software on the computer or handheld device to connect to a specific base station (or set of affiliate base
stations) after a user selects a network name from a list or manually
enters the network’s name. Mac OS X allows network selection from
the AirPort menu in the menu bar, the AirPort pane of the Internet
Connect program (located in the Applications folder), and the AirPort
view in the Network preference pane.
When a wireless adapter connects—technically, associates—with
a base station, the device to which the adapter is attached can send
data to and from the base station. If the base station has encryption
enabled, then an encryption key must be provided before the base
station allows the device access to any networks to which it connects.
Page 13
Depending on your setup, the key, a series of characters, must be
entered exactly as it was entered on the base station. A stored key
can be sent without a person having to re-enter it.
Avoid entering an encryption key manually: The AirPort
Extreme also now supports a simpler method that avoids key
entry altogether. See Use WPS.
Once an adapter connects to a base station and the encryption key
is accepted, the computer’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.
The Spectrum Part of Wi-Fi
Wi-Fi networks use unlicensed spectrum, so called because regulatory
agencies don’t require users to obtain a license to use those airwaves,
and everyone may use that spectrum; cellular telephone companies,
by contrast, pay huge amounts for the exclusive geographic rights to
certain frequencies.
Unlicensed bands—specified ranges of frequencies—are divided into
smaller upper and lower bounds called channels, which allow many
devices to use the same band within “hearing” distance of each other,
but without overlapping any or all the frequencies they employ. However, unlicensed bands are intended for broad use by individuals and
businesses, and there’s no guarantee that you and other people won’t
produce interfering signals, reducing the speeds you can achieve.
The rule is that in these unlicensed bands, devices use extremely low
signal power, but they also must be quite robust in order to cope with
lots of interference while still functioning.
In the United States and in most countries, the 2.4 GHz (gigahertz)
and 5 GHz bands are available for use. (The 900 MHz [megahertz]
band is also unlicensed in the United States, but it is not employed
for wireless LANs.) The precise frequencies and channels vary enormously by country. Older AirPort equipment could work only in
the 2.4 GHz band; the 2007 version of the AirPort Extreme and
the 802.11n protocol can use either the 2.4 or 5 GHz band.
Page 14
Warning! Apple and other manufacturers limit the usable channels and power output levels of Wi-Fi devices to what’s legal in the
country in which the gear is sold. Using that equipment outside the
country of purchase without first checking on what’s legal could
result in fines or jail time.
NOTE In some countries, the 4.9 GHz band is used instead of the 5 GHz
band; in the United States, 4.9 GHz is a restricted band, partly
devoted to fire, emergency, and police digital communications.
Wi-Fi and AirPort Flavors
AirPort hardware has gone through many transformations since
its original 1999 introduction. Each major flavor of Wi-Fi that Apple
has built into AirPort gear relies on industry standards created by the
IEEE, the Institute of Electrical and Electronics Engineers. The IEEE
has groups that work on many different kinds of standards. Their 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. For instance,
the original popular flavor of Wi-Fi was known as 802.11b or just “B”
for short. The current fastest generation is known as 802.11n or “N,”
and is still being finalized even as Apple and others have released
equipment that uses a draft of the standard, often called “Draft N”
(see Not yet finished, for more detail).
The Wi-Fi Alliance takes those IEEE standards and builds tests that
allow different makers to ensure that they are creating equipment
that works with all the other manufacturers’ equipment and that
carries out a common set of tasks in the same way.
Since the original AirPort in 1999, Apple has released three major
versions of AirPort hardware, which correspond to three major revisions of the IEEE 802.11 standards (Table 1, next page). Every older
version can be used with even the newest flavors. Let’s look at those
older flavors, briefly, and then focus on Apple’s newer 802.11n gear.
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Table 1: Wi-Fi Standards in Apple Hardware
Apple Equipment
(introduced, discontinued)
802.11b (B)
• AirPort (1999, discontinued 2003)
11 Mbps
5.5 Mbps
54 Mbps
25 Mbps
300 Mbps
90 Mbps
(with Feb.
2007 base
• AirPort Card (1999, discontinued 2004)
802.11g (G)
• AirPort Extreme
(2003, discontinued 2007)
• AirPort Extreme Card
(2003, superceded by built-in adapters,
but not discontinued at this writing)
• AirPort Express (2004)
• Built-in 802.11g adapter in Macs (2005)
• iPhone (June 2007)
• AirPort Extreme (Feb. 2007)
(N or Draft N)
• Apple TV (Feb. 2007)
• AirPort Extreme with gigabit Ethernet
(Aug. 2007)
• Built-in 802.11n adapter in all current
model desktop, laptop Macs (late
140 Mbps
(with gigabit
* Current draft became a tested part of Wi-Fi in June 2007; final version is due in September
2008 in a very similar form.
** Intel Core 2 Duo Macs except discontinued 1.83 GHz iMac and all Mac minis; optional
adapter for the Mac Pro.
Original AirPort (1999)
The original AirPort system uses 802.11b, and it comprises an AirPort
Card, which fits into a card slot in all AirPort-capable Macs released
through 2002; and an AirPort Base Station, which resembles a small,
gray (“graphite” original) or white (“snow” revision) flying saucer.
The graphite base station has a single Ethernet port and a built-in
modem; you couldn’t connect the graphite model to an Ethernet LAN
and WAN at the same time. The snow base station added a second
Ethernet port, which increased security and flexibility by allowing
Page 16
you to separate a LAN from a broadband or wide area network
(WAN) connection via a cable or DSL modem.
AirPort Extreme (2003)
AirPort Extreme 2003 uses the 802.11g standard. AirPort Extreme
originally appeared in two components: the AirPort Extreme Card
that fit into a new kind of internal card slot, and the AirPort Extreme
Base Station. The Base Station has the previous generation’s spaceship shape, is translucent white, and has three white LEDs for status
on the front.
Apple started adding the Extreme card slot to Macs released starting
in January 2003, and completed the transition by September 2003.
By 2006, all Macs included AirPort Extreme as a built-in feature
except for the Intel Xeon Mac Pro, which has the option to be factory
equipped with Wi-Fi, and the Xserve, which is designed for server
rooms. (Bluetooth came to be included in all but those two models,
too, by 2006.)
Apple quietly added 802.11a—which uses a different frequency band
and is explained later—to the Intel line of Macintoshes, but never
explicitly advertised this fact or offered support. See Apple’s version
of 802.11n for why this is useful.
Card or built-in? Apple moved from offering Macintoshes with
an AirPort Extreme card slot to including Wi-Fi onboard—but
they still call the technology AirPort Extreme, and they still sell
the standalone card for older Macs.
AirPort Express (2004)
The AirPort Express Base Station, which started shipping in July
2004, is similar to the AirPort Extreme Base Station, but it supports
fewer users and can stream music to a stereo. A single yellow/green
LED shows the unit’s status. The Express is still sold as this book
goes into production.
AirPort Extreme (2007)
At Macworld Expo 2007, Apple quietly moved the AirPort Extreme
Base Station from 802.11g to 802.11n. They announced that most
current Macs could have 802.11n enabled through a firmware update,
and they revealed a new AirPort Extreme that started shipping in
February 2007. This unit had just 10/100 Mbps Ethernet built in.
Page 17
In August 2007, Apple released an updated unit, keeping the same
name but adding gigabit Ethernet.
Because Apple has unfortunately kept the name the same for both of
these new units, to avoid confusion, I call the new base station models
collectively “Extreme N” where Ethernet speed doesn’t matter. When
Ethernet makes a difference in performance or features, I call the
February 2007 model “Extreme N (original)” and the August 2007
model “Extreme N (gigabit).”
This new base station has a square footprint, is squat, and is designed
to be stacked, making it easy to distinguish visually from the spaceship shape of previous base stations.
Extreme N Details
Let’s learn more about the new Extreme N base station and Extreme
N AirPort adapters.
802.11n technology
802.11n is up to seven times faster than G in typical circumstances
when measuring real data passed over a network. N uses several
antennas, with at least two receiving and two transmitting data, as
well as multiple radios. Each radio can transmit data while varying
the amount of power on each transmitting antenna, thus steering
the radio beam. This allows signals to go farther, and allows multiple
simultaneous data streams—each radio sending a unique set of data
at the same time over the same frequencies!
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 allow 802.11n to have a raw data rate of 300 Mbps
in a basic version and up to 600 Mbps in advanced versions. The
Extreme N and other consumer gateways will almost all use the
300 Mbps speed, which can pass as much as 150 Mbps in real data.
The speed drops when other Wi-Fi networks are in use in the vicinity,
when older 802.11 devices are used on the same network, or when N
adapters are far enough away from the base station to require slower
transmission rates.
Page 18
Not yet finished
An important proviso when discussing 802.11n is that the standard
isn’t finished. As with some earlier 802.11 standards, the work has
taken so long in the IEEE 802.11n task group that companies and the
Wi-Fi Alliance have moved forward while the details are being settled.
That led to a lot of equipment working at its best speeds only when
exchanging data with other devices made by the same company and
using the same Wi-Fi chips.
Draft N, as it’s known, spent 2006 in limbo, while companies and
engineers engaged in horse trading in order come up with something
the whole industry liked. Draft 2.0 was accepted by the IEEE’s
wireless networking group in March 2007, and the Wi-Fi Alliance
developed a set of interim interoperability tests in June 2007 to
certify equipment as complying with Draft 2.0.
Most major hardware vendors have had pre-production versions
of their Draft N hardware approved by the Wi-Fi Alliance to carry
their Draft N seal of approval. However, the testing happens on
engineering models; firmware still must move into production
and then be released as updates by hardware makers.
In early September 2007, Apple released its certified Draft N firmware update for Extreme N. By the time you read this book, many
other companies’ products should also have certified Draft 2.0
firmware available for download. That new firmware should, in
turn, allow the highest possible speeds among all Draft 2.0 gear.
Apple’s version of 802.11n
The Extreme N is the first base station released by Apple that
supports both major frequency bands for Wi-Fi: 2.4 gigahertz (GHz)
and 5 GHz. While 2.4 GHz is better known, and has been used by
the original plain 802.11 spec, as well as B and G, the 5 GHz band
has been available for some time, waiting for the right technology
to make use of its wide-open spectrum.
Page 19
NOTE A little-used 802.11 protocol known as 802.11a, or “A,” was
famously declared dead by Steve Jobs in January 2003. The A
protocol never took off because while it had the advantage of using
the 5 GHz band, it wasn’t backward compatible with the popular B
protocol, which is still in wide use. Some organizations chose to use
A for voice over IP (VoIP) for that very reason: they could use the
5 GHz band with little interference.
Apple slipped 802.11a into the Intel versions of its Macs without
advertising the fact because the Intel chips Apple used included
802.11a at essentially no additional cost. Since there were so few
802.11a base stations available—almost none for consumers—the
fact seemed unimportant.
The 5 GHz band in the United States offers 23 non-overlapping
channels for 802.11a/n; whereas the 2.4 GHz band offers only 11
staggered, overlapping channels for 802.11b/g. Further, the 5 GHz
band has many fewer users.
Tune in tomorrow: Apple has chosen to allow use of just eight
of those 5 GHz channels at present, but future firmware could
easily up the total to 23. The company told me in August 2007
that they are investigating adding more channels but had no
specific plans nor timetable. When and if that happens, I’ll post
information on this book’s update page; click the Check for
Updates link on the cover to visit that page.
Warning! Apple sells specifically tailored versions of its Extreme
N for different parts of the world. This is especially significant due
to how the 5 GHz band is regulated in each country. If you buy a
North American Extreme N and take it to, say, France, as one of
my colleagues did, when you power it up, you’re likely in violation
of local law. If you happened to tread on local uses, including
military purposes, you could be found (via triangulation) and
spend some years in jail.
Apple could have supported just 2.4 GHz in the new 802.11n gear
for backward compatibility, but instead the new gear supports both
bands, which offers a lot of potential for maximizing the speed of
a network, even in the home. (See Mix Legacy, New N Networks.)
Page 20
Physical features
The latest base station (Figure 1) is square, designed for stacking,
with the same footprint as a Mac mini (6.5 inches/16.5 cm square),
and a smaller footprint than the Apple TV (7.7 inches/19.7 cm
square). (The Apple TV is 1.1 inches/2.8 cm tall; the Mac mini,
2 inches/5.1 cm; and the Extreme N, 1.3 inches/3.4 cm.)
The tilted front view (left) and straight-on back view (right) of the
AirPort Extreme Base Station introduced in 2007. The back ports are,
left to right, power, USB, one WAN Ethernet jack, three LAN Ethernet
jacks, and a security slot for physical lock-down.
The Extreme N base station is the first to offer an Ethernet switch;
Apple included four Ethernet ports, three of which are used for the
LAN and one for the WAN. The Extreme N (original) included 10/100
Mbps Ethernet. The N standard can outstrip 100 Mbps Ethernet,
which achieves somewhere over 90 Mbps of real throughput. That’s
the reason why in August 2007, Apple released the Extreme N
(gigabit) with 1,000 Mbps Ethernet on all four ports. In the process,
Apple improved throughput in nearly every configuration I tested.
Hardware, not software: Before you ask, the earlier Extreme
Ns can’t be upgraded to support gigabit Ethernet. Okay, it’s a
reasonable question, given that Apple’s 802.11n was included but
not turned on, in some Macs. To add gigabit Ethernet, Apple used
different chips in the second model of the Extreme N.
Fastest method: If you really need speed, gigabit Ethernet is
far faster and simpler than Wi-Fi, with the only downside being
the requirement for wires. Ethernet switches can deliver nearly
seven times the throughput of N 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.
Page 21
Adapters in Macs
Starting around the end of the third quarter of 2006, Apple began
introducing new Mac models that secretly included 802.11n wireless
chips. Apple didn’t tell customers or enable the faster N mode, so the
Macs behaved like they had a G card inside. Apple was apparently
waiting for the standard’s progress to be clear before switching on the
new 802.11n capabilities. (Clever buyers who cracked their Macs open
figured this out long before Apple made it official.)
This set of computers comprises:
• All Macs with Wi-Fi adapters and Intel Core 2 Duo processors—
except the 17-inch, 1.83 GHz iMac , which was discontinued in
August 2007, and the Mac mini. (Those exceptions have 802.11a,
• The Xeon Mac Pro, if you chose the wireless add-on option.
Enable your Mac! Apple didn’t start enabling 802.11n on Macs
until as late as third-quarter 2007. So, depending on when your
Mac entered the retail channel, it may, or may not, need you to
enable 802.11n. (Find out if you Mac needs to be enabled in the
sidebar Do You Need the 802.11n Enabler?)
To enable a Mac, you must install the AirPort Extreme 802.11n
Enabler for Mac. You can install it from the CD that ships with the
Extreme N, as I describe in Install new software. You can also buy
it from the Apple Store separately for $1.99. Once you own a copy
of the enabler, you can use it on “all computers under your ownership or control,” as Apple’s licensing terms put it.
Third-party adapters
Apple didn’t offer—and never will offer—N on the separately
installable AirPort Extreme Card. About 3 years ago, Apple began
including the 802.11g AirPort Extreme as a basic design feature on
new Macs. Without Wi-Fi being on a separate card, Apple had little
motivation to provide an upgrade. They’d rather you buy a newer
computer, if you really need 802.11n.
Third parties are starting to step up to the plate, however, with
QuickerTek the first out of the gate and Other World Computing
following at their heels.
Page 22
The company has released several adapters in its nQuicky series
and under other names (http://www.quickertek.com/). Some options
remain expensive (at this writing) because of the higher engineering
cost and higher chip costs associated with N right now. Expect prices
to drop. The nQuicky models and the nNano all support just 2.4 GHz,
which reduces potential throughput.
The nNano is a $59.95 USB adapter that works with all Macs running
Mac OS X 10.3 or higher; they’re also offering the $49.95 Nano,
which is 802.11g only, useful for Macs that could otherwise operate
only at 802.11b speeds with a hard-to-obtain original AirPort Card.
The nQuicky USB ($149.95), nQuicky PCI ($99.95), and nQuicky
CardBus ($64.95) all require Mac OS X 10.3.9 or later. The USB
model works with any Mac, and it has a much higher-gain antenna
than the nNano; the PCI works with all Power Macs (G3, G4, and G5)
except the G5 models that use DDR2 (double data rate, 2nd version)
memory; and the CardBus adapter supports any PowerBook.
For Intel Macs issued without Draft N hardware, QuickerTek offers
hardware updates that require opening a case and messing about.
They’ll also perform the upgrade for you. Prices for the kit and the
mail-in install (exclusive of return shipping) are: MacBook or
MacBook Pro, $99.95/$149.95; Mac mini or iMac, $179.95/$199.95.
Finally, if you have a Mac mini, QuickerTek offers a kit and mail-in
install ($149.95/$199.95) that swaps in 802.11a for 5 GHz and
802.11n for 2.4 GHz. It’s an odd option, but could be useful.
Other World Computing
Other World Computing has also released a set of 802.11n adapters
that work in the 2.4 GHz band: a PCI Card for Power Macs, a PC
Card for PowerBooks, and a USB adapter for any Mac that can run
Mac OS X 10.3 or later (http://eshop.macsales.com/shop/wireless/).
All three adapters in their Edimax nMax series cost $67.99, and work
with Windows XP/2000 and later, too.
A unique aspect to the Edimax adapters is that they support wide
channels in 2.4 GHz. Because Apple doesn't offer wide 2.4 GHz
channels, you would need a Wi-Fi gateway from another company
to take advantage of that option, which isn't considered particularly
advantageous in 2.4 GHz, anyway.
Page 23
More coming soon
I expect that other vendors will add Mac OS X drivers, too, as many
have with each previous generation of Wi-Fi hardware. Belkin, a
stalwart provider of Wi-Fi and other peripherals with Mac OS X
drivers, told me fairly strongly that Mac OS X drivers are coming for
their equipment. Ralink is likely, too, as are firms that resell products
using Atheros chips (Atheros is Apple’s chip supplier for Wi-Fi).
Compatibility among AirPort Generations
Each AirPort generation is backward compatible with all previous
generations, although backward compatibility can be turned off.
While the original AirPort handled just 802.11b, AirPort Extreme
2003 added 802.11g, which incorporates B with full support. Likewise, Extreme N’s 802.11n handles the older A, B, and G standards.
However, transfer speeds between an adapter and a base station
running different 802.11 standards can’t exceed the speed supported
by the slower of the two 802.11 flavors that both devices share. A B
device connecting to an N base station communicates at B speeds,
meaning that each packet of data a B device pushes through the
network occupies the equivalent of 10 to 20 N packets.
While most of the loss in throughput happens only while older
devices are taking up airtime (and newer devices are cooling their
heels), simply enabling backward compatibility shaves at least
10 percent off the maximum throughput of the network. This overhead comes from the fact that every computer on the network must
send extra traffic that’s designed for older devices to interpret.
NOTE Wi-Fi gateways can force older adapters to talk less. In one method,
an 802.11n gateway would use an existing mechanism that all the
standards understand to grab an equal amount of time as a B
device, rather than an equal amount of data. These mechanisms
aren’t standardized yet, and it’s unclear if Apple has implemented
any of them. In the future, it’s likely that we’ll see this kind of
protection against older devices hogging a network.
One way to avoid bogging down an N network is to set the N network
up as a new, separate entity, leaving an older, slower B or G network in
place. I discuss how to set this up in Mix Legacy, New N Networks.
Page 24
You’re ready to set up your network, so let’s get unpacking! This
section focuses on initial setup, and in many cases it will take you
to a working Wi-Fi network. But, if you need to go beyond the basics,
you can keep reading beyond this section to learn about special cases
in configuring your local and wider network connections. Also, note
that Connect Your Computers, later, explains how to connect via WiFi from any computer in the vicinity to the newly set up base station.
Although one base station must be connected with Ethernet to
your Internet connection, you can connect AirPort Extreme—both
G and N models—and AirPort Express Base Stations wirelessly back
to that main base station. For setting up these satellites, see Bridge
Wirelessly for step-by-step details.
Set Up Your Base Station
Let’s get that base station out of its box, plugged in, and ready to
connect to the Internet.
Unpack and power your base station
The Extreme N comes with fewer parts than any previous Apple base
station. Unpack the base station to determine what you have and if
you need any additional hardware:
• Remove your base station from its box and check the
parts. The Extreme N box includes just a few necessary parts:
The square base station, a CD containing utility and enabler
software, and a power adapter and its corresponding AC power
cord. The base station no longer comes with a wall-mounting
bracket; it’s designed to work horizontally.
• Is the power cord long enough? The power cord’s length—
17 feet/5.2 m—should aid in placement; in the American version,
the AC end of the cord terminates in a non-polarized two-prong
plug—both prongs are the same width—which can work in any
outlet in either orientation. That still may not be long enough,
so plan on purchasing a lightweight extension cord if you need
to place the base station more than 17 feet/5.2 m from an outlet.
Page 25
This model doesn’t have a wall-mounting bracket because it works
best level on a table or floor. (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 for Your Base Station before
you continue.)
• Get Ethernet cables. The Extreme N, unlike its predecessors,
comes with no network cables. Configuring your base station
may be simpler if you hook it to your computer or existing LAN
with an Ethernet cable, and you need at least one Ethernet cable
in the likely case that you plan to connect the base station to a
broadband router or other network. The Extreme N has autosensing, auto-switching Ethernet, which means you needn’t buy
particular kinds of Ethernet cables. I recommend Cyberguys.com
as a good online source for cables (http://www.cyberguys.com/).
Configuration Computer: You’ll be using AirPort Utility to
configure your base station, and the steps I give shortly show
screenshots taken on a Macintosh. To configure from a Mac, you
must be running Mac OS X 10.4.8 or later. However, AirPort
Utility can also be installed under Windows XP or Vista, and the
steps are the same.
Now it’s time to power up. Plug your base station into an electrical
outlet, and plug an Ethernet cable from your computer into any of the
three LAN ports. If you’d rather have mobility while configuring, you
can also set up the base station via Wi-Fi, but you will have to keep
reconnecting after each configuration change if you change password
and naming options.
Flashy: In a neat addition, all the Ethernet ports on an Extreme
N have a tiny green LED that lights up when an Ethernet cable is
connected to the port and there is a live connection on the other
end of the cable; the LED flashes to indicate activity. A front
green/amber LED shows the status of the base station, including
activity (green) or trouble (amber).
I recommend not connecting your 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.
Page 26
Install new software
The Extreme N comes with a CD full of software: AirPort Utility,
AirPort Disk Utility, and the 802.11n enabler for appropriately
equipped Macs. The software isn’t—at this writing—available for
download from Apple’s Web site. AirPort Utility replaces the hoary
AirPort Admin Utility, which dates back to 1999; the new AirPort
Utility combines a set of assistants with advanced configuration
options (Figure 2). It can configure any AirPort Extreme or AirPort
Express base station.
No advantage for older base stations: AirPort Utility is
different, not better, than the older AirPort Admin Utility. There’s
no particular reason for those of you without an Extreme N to use
the newer software.
TIP If you’re still using an old graphite or snow base station, the AirPort
Admin Utility isn’t deleted; it’s renamed AirPort Admin Utility for
Graphite and Snow (find it in /Applications/Utilities).
The main screen of the new AirPort Utility.
Page 27
On a Mac running Mac OS X 10.4.8 or later, or with Windows XP
or Vista, run the installer on the CD.
While installing, on the Installation Type screen, you can click the
Customize button to install individual utilities or components. The
full installation includes:
• AirPort Utility, which you need to configure your Extreme N base
• AirPort Disk Utility (called AirPort Disk on the Custom Install
screen), which lets you mount hard disks and partitions that are
connected via USB to an Extreme N.
• AirPort Base Station Agent, a monitoring program that can alert
you when there’s a problem with an Extreme N on the local
• The 802.11n enabler, (it’s called AirPort Extreme Drivers on the
Custom Install Screen), which turns on the N support in Macs that
have the correct chips. It’s installed only on computers that need
it. All newly purchased Macs that were described as including
802.11n are already enabled for that flavor of Wi-Fi; if you bought
a Mac before August 2007, see the sidebar Do You need the
802.11n Enabler?, next page.
The last step of the installation is to restart the computer.
Page 28
You can check if you need to install the enabler on your Mac by
launching Network Utility from /Applications/Utilities
and choosing the appropriate interface from the pop-up menu at
the top of the Info pane, usually “Network Interface (en1)”. If the
computer doesn’t require the update, “(802.11a/b/g/n)” appears
under Wireless Network Adapter at the bottom (Figure 3).
If only “(802.11a/b/g) is shown, run the enabler and restart, and
then check Network Utility again.
Network Utility shows that the 802.11n enabler
isn’t needed.
After restarting, you can find AirPort Utility and AirPort Disk Utility
in /Applications/Utilities.
Run the installer on every computer on your network that has an
802.11n adapter that needs to be upgraded, from which you want
to mount hard disks connected to the base station, or with which
you want to configure the base station.
Launch AirPort Utility and let’s get this AirPort on the air!
Keep up to date
The first time you run AirPort Utility, it prompts you to choose
whether or not to check for updates automatically. Although Mac
OS X’s Software Update feature (Apple > Software Update) will also
alert you to install AirPort software and firmware releases, Apple set
Page 29
up this separate update conduit to make it more likely that you would
apply security, stability, and compatibility upgrades that you might
otherwise ignore for a while in Software Update.
This update notification works whether or not you have AirPort
Utility launched. The AirPort Base Station Agent, added as part of
the AirPort Base Station Update 2007-002 (for Mac and Windows)
in August 2007, monitors at the frequency you specify for updates,
and then launches AirPort Utility if an update is available.
You can adjust the frequency for which updates are checked in
AirPort Utility’s Preferences dialog (Figure 4).
AirPort Utility
can check
for AirPortspecific software releases
from Software
Update (top).
The Summary
view also alerts
you when an
upgrade is
Connect to your base station
AirPort Utility is your one-stop shop for setting up the base station’s
parameters. But, first, you need to make a network connection to your
base station so that AirPort Utility can access it. With AirPort Utility
launched, use one of these three methods to find your base station;
the methods are listed in order of simplicity:
• Connect via LAN: In the simplest case, you use an Ethernet
cable to plug your computer into one of the three LAN Ethernet
ports on the Extreme N. The unconfigured base station should
appear in the left column of AirPort utility (Figure 5), confirming
that you’ve made the connection.
Page 30
An unconfigured base station appears
in AirPort Utility’s base station list
named uniquely with the last six digits
of its AirPort ID (see the note, “Default
Network Names,” below). (Dig the
subtle reflection!)
• Connect via a larger network: For larger LANs, in which the
base station is just a piece of the network, you can connect the base
station to your larger LAN through the base station’s WAN port,
connecting an Ethernet cable from it to any port on an Ethernet
switch on your network. Because the base station uses Apple’s
Bonjour, a way for devices to advertise their availability across a
network, you should be able to spot the new base station in AirPort
Utility even though it hasn’t been configured. Failing that, try
configuring with Wi-Fi.
• Connect via Wi-Fi: Slightly trickier is connecting via Wi-Fi,
because many configuration changes require that you apply new
settings by clicking Update in AirPort Utility. This restarts the base
station and thus you have to reconnect to it.
From the factory, Extreme N is set to 2.4 GHz, so you can initially
configure it via Wi-Fi from any computer. An unconfigured base
station shows up with a default Wi-Fi network name in the AirPort
menu (see “Default Network Names,” below).
The default Wi-Fi network name for Extreme N base stations—
as well as previous base station models—is AirPort Network
0033FF where 0033FF is replaced with the last six digits of the
AirPort ID of the wireless adapter in the Extreme N. The default
Ethernet network name is Base Station plus a space and then
the last six digits of the AirPort ID. That ID is printed on the
underside of an Extreme N.
The AirPort ID is a MAC (Media Access Control) address. See What
and Where Is a MAC Address? (p. 59) for more information about
MAC addresses.
Page 31
Handle initial setup
The simplest way to configure a base station is to use AirPort Utility’s
built-in assistant, which walks you through assigning a name to the
base station, changing its administrative password, and turning on
encryption. (If you are reconfiguring a base station, see Reconfiguring
a base station, ahead.)
Follow these steps to configure your base station:
1. In AirPort Utility, select the base station from the list of base
stations at the left.
2. On the “Welcome to AirPort Utility” screen, click Continue to open
the first Network Setup screen (Figure 6).
Enter a
network and
base station
Screen names: The assistant screens lack unique names; look in
the title bar of each window for the name of the screen. I’ll give
you other cues, too.
3. Enter a network name and base station name:
• The network name will be “advertised” to Wi-Fi adapters that
scan for networks to connect to; for instance, on a Macintosh
the network name will appear in the AirPort status menu at the
right of the menu bar. Multiple base stations may share the
same network name to create a network with a larger area
or more available bandwidth.
• The base station name will be used to identify the base station
in AirPort Utility.
Page 32
Once you’ve entered both names, click Continue.
4. On the second Network Setup screen (Figure 7), choose the
country in which the base station will operate and the backward
compatibility you need, and click Continue.
Choose your
country and
Almost anyone reading this book will want to choose United States
or Puerto Rico, and leave the radio button next to Radio Mode set
to “802.11n (802.11b/g compatible)”. (For more about spectrum
and country choices, see Configure the Spectrum and Channel.)
Warning! Do not use the AirPort Extreme in a country that’s
not listed in the Country pop-up menu. It’s not just a suggestion;
national regulators monitor for misuse and you could wind up
in the pokey, or worse.
5. On the third Network Setup screen (Figure 8), select the level
of security you want to use:
• WEP allows the oldest Wi-Fi adapters to connect to a network.
• WPA2 is actually mixed WPA/WPA2 security, which allows
Macs running Mac OS 10.3 Panther or later and computers with
Windows XP SP2 or later to connect.
• No security allows all connections.
Warning! Apple’s explanation on this screen about how WPA
and WPA2 work is a little breezy, and it could frustrate you
when trying to connect some older Macs to the network. The
Use Built-In Encryption section can help you avoid that
Page 33
Select your security option, and click Continue.
to prevent
6. The first Internet Setup screen lets you choose how addresses are
assigned on your network (Figure 9). The four options cover the
major scenarios, which you then configure in the next step:
• DSL or cable modem with static IP address or DHCP:
This is the right choice in almost every case.
Most broadband providers use DHCP to assign your base station
an address automatically. (DHCP and the corresponding NAT
feature are explained in detail in Hand Out LAN Addresses.)
A static IP address requires additional manual entry. (A static
IP address is a fixed IP address that your service provider
provides to you.)
• DSL or cable modem with PPPoE: This option works with
ISPs that use a special log in that the base station has to handle.
The login process lets an ISP server assign an address (static or
dynamic) to your base station.
• LAN: For larger networks, this is the right option, because
you’ll set up networking values based on what you chose
yourself or use those provided by a network administrator.
Page 34
• Not ready: Apple provides this choice so you can configure
the rest of the settings without having to gather details for the
Internet setup.
• Modem: A modem option appears but is dimmed for Extreme
N base stations. If you’re configuring an older Extreme G with a
modem, that option’s available.
Confirm your selection and click Continue.
the kind of
exactly or
close to your
set up.
7. In the second Internet Setup screen, configure the TCP/IP
connection that allows your base station to access the Internet:
• If you chose the first (DSL/cable with static or DHCP address)
or third (LAN) option in the previous step, you have two
If you aren’t sure, or your ISP told you to, choose Using
DHCP from the Configure IPv4 pop-up menu. This option
is what most people choose.
If your base station is assigned a static address, with details
provided by your ISP or network administrator, choose
Manually from the Configure IPv4 pop-up menu.
Page 35
• If your provider uses PPPoE, enter the account name, password,
and optionally the service provider’s name, while choosing to
have the connection always on (default), automatic (connects
when needed), or manual (connects when you choose).
For more details, see Set Up Your Network. Click Continue.
8. The USB Peripherals Setup screen lets you set your initial password configuration for attached hard disks that can be shared via
the Extreme N. For details on these choices, see Set Up a Shared
USB Disk. The preselected options are fine; click Continue.
9. On the AirPort Extreme Setup screen, set up a base-station password. This password is unrelated to network data encryption and
protection, but it’s vital to set the password to prevent unwanted
access by others to the base station. The default base station passwords for all Wi-Fi routers are well known. Use a password that
is simple, but hard to guess.
I recommend checking the Remember the Password in My
Keychain option so that you can invent a password here and have
the system store it.
Click Continue when you are ready to move to the next screen.
10. The Summary screen shows all your choices (Figure 10). You
can click Go Back repeatedly to change options, or Update to store
your options and restart the base station with those new settings.
If you’ve forgotten the passwords you entered, click the Show
Passwords button first to see them in plain text so you can copy
them or write them down.
NOTE Whenever you click Update in AirPort Utility, the program sends
your configuration changes to the base station, which burns those
changes into non-volatile memory. Removing power from the base
station doesn’t cause it to lose these settings.
Page 36
A summary
the choices
you made
Reconfiguring a base station
You can reconfigure a base station that’s already set up by selecting
the base station in AirPort Utility and choosing Base Station > Assist
You can reset an Extreme N to its factory settings at any time
through software or hardware. Resetting the Extreme loses all
settings you’ve applied, including passwords. If you save a configuration (see Export and import configuration profiles), you
can load that configuration after resetting the base station.
Via software, launch AirPort Utility, select your base station, and
choose Manual Setup or press Command-L. From the Base Station
menu, choose Restore Default Settings. Click Restore in the dialog
that appears and wait for the base station to restart.
If you can’t connect to the base station or prefer the hardware
approach, use a ballpoint pen or the tip of a straightened end of a
paperclip to press the reset button for at least 5 seconds. The tiny
reset button is on the Ethernet connection end of the Extreme,
beneath a white right-pointing arrow in a field of gray.
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Create and manage profiles
The Extreme N carries over a feature, first found in the AirPort
Express, which allows you to define and store multiple profiles. A
profile is a complete set of configuration parameters; each profile
resides on the base station in non-volatile memory.
Stored versus exported profile: I call this form of profile
a “stored” profile to distinguish it from the “exported” profile
described just below.
These profiles can be useful when you’re sorting out precisely what
options you want for your network and want to create different
scenarios to test. Stored profiles are also useful if you take the base
station to different locations.
I suggest starting with a base profile that you can duplicate to test
other options, and then you can simply revert to it whenever you like.
Since you created the equivalent of a profile in following the steps
(just previously) for initial setup of an Extreme N, you can rename
that first profile to something descriptive and then duplicate it:
1. Select the base station in AirPort Utility, and then choose Base
Station > Manual Setup (Command-L).
2. Choose Base Station > Manage Profiles.
The screen that appears lets you create, activate, and delete
3. Click the
button to copy the current configuration to a new
You should now see another profile in the list. The AirPort Utility
also adds a Profile pop-up menu at the bottom of the screen.
4. Name the new profile: double-click the profile name to activate
the edit field, and then type a new name. Press Return to accept
the new name.
You can switch among profiles by choosing them from the Profiles
pop-up menu at the bottom of the manage profiles screen (Figure 11).
You must click Update to activate a given profile, or to save changes
that you make to the active profile.
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AirPort Utility lists stored profiles for a base station. To switch to a
different profile, choose the profile’s name from the Profiles pop-up
menu and click Update to restart the base station and load that
profile’s settings.
Export and import configuration profiles
There’s one more way you can work with profiles that you set up in
AirPort Utility: you can export current settings to a file that can be
imported later, for the same base station or for 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.
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Warning! Unlike stored profiles, these exported profiles do not
reside on the base station. However, profiles can be exported and
imported from any AirPort Extreme or AirPort Express base
station; stored profiles are available only with the Extreme N and
AirPort Express.
Management utilities will return: AirPort Management
Tools lets you manage several base stations at once, including
applying a model configuration file to them. However, it hasn’t
been updated at this writing for Extreme N. Apple told me it will
be updated at some point—although they told me that in February
2007, and the tools hadn’t returned when we published this
edition in September 2007.
To export a profile:
1. In AirPort Utility, select the base station from the list at the left,
and choose Base Station > Manual Setup (Command-L).
2. Choose File > Save a Copy As, and name the file descriptively, as
there will be few other clues that help you identify the file. (Apple
should have named this option Export Profile, since that’s the
action the menu item carries out.)
After you’ve exported a configuration file, you can open it within
AirPort Utility to examine the file’s list of settings without applying
those settings to an active base station. The settings appear in what
looks like a standalone AirPort Utility configuration window, but you
can’t apply the settings against a base station from that window.
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 profile:
1. In AirPort Utility, select the base station from the list at the left,
and choose Base Station > Manual Setup.
2. Choose File > Import. (See? For symmetry’s sake, you’d like Apple
to call the opposite operation Export!)
3. Select the configuration file and click Open.
4. Choose which options you want to import and click OK.
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Extreme N includes timed settings, which can restrict access to
given computers at given times of the day or week, and you can
choose to import just those restrictions, all settings, or all settings
except restrictions (Figure 12).
Select settings
to import.
5. Click Update to apply the imported profile’s settings.
Once the profile is imported, the settings replace your current base
station settings. This could confuse you if you’re also using stored
profiles: the imported profile modifies the active stored profile. These
changes take effect when you click Update.
TIP Importing just Timed Access Control settings lets you apply the
same restrictions for use across all base stations on a network, while
just setting those restrictions on a single base station.
Connecting remotely
You may want to set up remote access to your AirPort, so that you
can configure it via its WAN port—either from a larger network to
which the gateway is connected or elsewhere on the Internet. While
there are some risks associated with that, remote connections also
mean you can help, say, relatives, friends, or remote offices keep
their networks running.
To allow remote access, follow these steps:
1. In AirPort Utility, select the base station from the list at the left,
and choose Base Station > Manual Setup.
2. Click the Base Station button in the AirPort pane.
3. Check Allow Configuration over Ethernet WAN Port.
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With remote access on, AirPort Utility can now access a remote
Extreme N via its IP address or through a domain name if you’ve
assigned that name through DNS (Domain Name Service). To make
the connection, choose File > Configure Other and enter the IP
address or domain name.
Secure connection: I didn’t know if AirPort Utility creates
a secure, encrypted connection when you configure locally or
remotely. I looked at a packet dump of raw data while configuring a unit, and saw nothing intelligible, which typically means
that encryption is employed. I asked Apple, and they assured me
that they did the right thing: you can enter a base-station password and configure over a local or remote network without fear
of interception.
Configure the Spectrum and Channel
With the Extreme N, you’re faced with a choice: 2.4 GHz or 5 GHz?
That choice makes a huge difference in the overall performance of
your network, and how well it works with older machines.
Warning! With all the talk of Extreme N supporting two frequency bands, you might have thought that the base station could
work in both bands simultaneously. Not so; that would require
duplicating the whole radio function. Instead, you could set up
two separate, connected networks, one on each band; see Mix
Legacy, New N Networks.
Consider your spectrum choices
The 2.4 GHz band is crowded with other Wi-Fi networks, Bluetooth
devices, and other uses; 5 GHz is relatively empty—in the United
States, the band has almost seven times the amount of frequency
available in the 2.4 GHz band. Further, Apple restricts the use of socalled wide channels to the 5 GHz band. Wide channels use twice the
standard amount of spectrum and thus can achieve twice the data
throughput. Apple does this in order to avoid treading on older
networks in 2.4 GHz.
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In my tests comparing the two bands’ throughput—the net amount of
data passed over a network—I found that the 5 GHz band offered very
consistent throughput as high as 140 Mbps (N to Ethernet LAN) and
90 Mbps (N to N) because there were few other variables to control,
like other users or uses of the channels I tested. With 2.4 GHz,
however, throughput was all over the place. I could test the same
network setup over and over again, and sometimes see the highest
rates (about 70 Mbps, N to Ethernet LAN), and other times see rates
drop to 10–30 Mbps. See Table 2 for specifics.
Higher Wi-Fi rates require Extreme N (gigabit): To achieve
the highest speeds from the Extreme N, you must have the newer
gigabit Ethernet model.
Table 2: Throughput Based on Band Choice (Best Speeds)
2.4 GHz (regular channel)
5 GHz (wide channel)
Draft N to Draft N
(same Extreme N)
Up to 35 Mbps (from one
computer to another), but
varies enormously
Up to 90 Mbps (from one
computer to another); up to
50 Mbps with two computers
transmitting to each other
Draft N to wired 100
Mbps Ethernet (LAN)
Up to 70 Mbps, but varies
Over 90 Mbps
Draft N to gigabit
Ethernet (LAN)
Over 140 Mbps
Draft N to any Ethernet Up to 50 Mbps*
(WAN) with NAT
Any Ethernet (LAN) to
any Ethernet (WAN)
Up to 70 Mbps*
100 Mbps Ethernet
LAN to same LAN
94 Mbps
Gigabit Ethernet LAN
to same LAN
900 Mbps
* With NAT turned off, speeds are the same as Ethernet LAN.
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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 other approved uses that can conflict at times.
Industrial sealers, for instance, use heating processes that emit
2.4 GHz radiation. Home microwave ovens use the principle that
water molecules are dipolar (have two oppositely charged ends),
and they switch the fields 2.45 billion times a second to cause
friction which heats the food. (If your friends think microwaves
“leak” radiation, create ionizing radiation, or “irradiate” food,
please have them read this excellent Q&A page:
Problems with AirPort networks often stem from your own or
neighbors’ use of conflicting technology, which can include
2.4 GHz cordless phones, the above-mentioned microwave ovens,
nearby industrial sites, or wireless cameras. The 5 GHz band has
many fewer approved uses; primarily, 5.8 GHz cordless phones
will be your enemy.
The rising interest in a new wireless standard called WiMax could
be problematic. While WiMax will largely use licensed spectrum,
there’s plenty of interest and many early deployments that use
the 5.8 GHz band to carry data from one central transmitter to
many roof-mounted antennas.
You would think that the choice of using 5 GHz is obvious, right?
Not so fast. If you have any 802.11b or g devices on your network—
like Macs with the original AirPort Extreme built in—they can’t
connect. Or if a visitor were to show up with an older adapter, she
would be out of luck. On the other hand, if you have all Intel Macs,
you could use 5 GHz and mix A and N, which would provide much
better performance than mixing G and N in the 2.4 GHz band. See
Table 3 (next page) for a comparison of the tradeoffs.
You can get the best of both worlds if you have an existing 802.11b/g
network and want to add to the network, rather than replace it. See
Mix Legacy, New N Networks.
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Table 3: Comparing the 2.4 GHz and 5 GHz Bands
2.4 GHz
• Backward compatible with
802.11b/g devices
• Relatively crowded with other
users, purposes, including 2.4
GHz cordless phones, Bluetooth
• Longer range than 5 GHz
• Best for a network with a mix
of B or G, and N Wi-Fi adapters
• Third-party N adapters already
available for Macs, but only in
2.4 GHz
5 GHz
• Maximum data rate is about
70 Mbps (Wi-Fi to wired) or
50 Mbps (Wi-Fi to Wi-Fi) only in
the best conditions
• Throughput can be very poor,
connection erratic
• Allows wide channels for higher
• Can’t work with 802.11b/g
• Maximum data rate is 140
Mbps (Wi-Fi to wired) or 90
Mbps (Wi-Fi to Wi-Fi) in normal
• Higher attenuation than 2.4 GHz
means signal strength drops
faster when passing through
walls, floors, even people
• Relatively uncrowded, very
large band, with lots of room to
move to other channels
• 5.8 GHz cordless phones and
some unlicensed WiMax
networks can interfere, reducing
the number of possible channels
• Backward compatible with
802.11a found in Intel Macs
and some Windows laptops
• No need to slow down for B
• Best for all-new network with
no visitors expected
Second to choosing your spectrum is choosing a channel. The regular
and wide channels I mentioned earlier are schemes to allow many
networks to work together in overlapping locations. Regular channels
use 20 MHz of spectrum; wide channels use 40 MHz.
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MHz and Mb: Megahertz does, in fact, correlate to megabits
per second. Shannon’s Law, 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.
In case you were wondering, the formula is: maximum bit rate
equals channel width in hertz multiplied by log2 multiplied by the
sum of 1 + signal divided by noise.
In the United States, 802.11 standards can use any of 11 numbered,
staggered channels in the 2.4 GHz band (Figure 13). 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
when you want the least interference. (In some countries, the 2.4 GHz
band is slightly wider, allowing for four non-overlapping channels.)
Also, due to the overlapping, staggered nature of the channels, there
is room 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.
2.4 GHz 802.11 channels are staggered, with channels 1, 6, and 11
having the least overlap. 5 GHz 802.11 channels are meant to have
little overlap; only the four lowest channels of 23 are shown.
By contrast, the 5 GHz band can be divided into 23 channels for
802.11a or n. The regular-width channels are the same 20 MHz width
as 2.4 GHz band channels; or you can use 11 wide channels that are
Page 46
40 MHz wide. These channels overlap only at the fringes, and thus
allow many different networks to work in the same space with little
NOTE Unlike the 2.4 GHz channels, which are numbered sequentially—
1 to 11 in the United States—5 GHz channels jump by an increment
of four and don’t proceed sequentially. Why? Two reasons:
• First, 802.11 channels—for A, B, G, and N—increment by 1 for
each unit of 5 MHz. Because 802.11a/n channels don’t overlap,
you get four numbers (20 MHz) between each regular-width
• Second, 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 802.11a or n.
Unfortunately, for reasons that are still not publicly stated, Apple
has chosen to offer only 8 of the 23 possible 5 GHz 802.11a/n
channels for use. The 15 that they aren’t supporting have specific
restrictions on use.
A few years ago, the IEEE developed 802.11h to allow the A spec
to work in Europe. This 802.11h addition allows better co-existence
between some existing uses of 5 GHz, like military radar, and it’s
become a necessary part of N as well. More recently, a compromise
between the electronics industry and the military opened up 255 MHz
of additional spectrum in the 5 GHz band—11 A/N regular channels—
but using the additional spectrum requires that you use 802.11h not
only for those new channels but also for four of the existing ones.
Between European restrictions and the availability of more channels,
it’s even more peculiar that Apple has released a worldwide product
without fully taking advantage of all the possible channels.
Apple’s Wi-Fi chip suppliers support this co-existence. One chip
vendor told me that Apple could add the missing channels through
a simple firmware upgrade. Apple told me in August 2007 that they
were actively investigating adding additional channels, but had no
timetable or specific plan to do so.
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Set a band and a channel
To configure which band you use, and what backward compatibility
your base station offers, launch AirPort Utility, connect to your base
station, and choose Base Station > Manual Setup. Click the AirPort
icon to open the AirPort pane, and then click the Wireless button.
The Radio Mode pop-up menu offers four choices:
• 802.11n (802.11b/g compatible): This mode allows full
backward compatibility in 2.4 GHz, while allowing N to work at
about 70 percent of its full speed in regular-width channels.
• 802.11n (2.4 GHz): With this choice, your base station supports
only N devices, and B and G devices can’t connect to it.
• 802.11n (802.11a compatible): This 5 GHz mode could be
useful if you have all Intel Macs on your network and you want
the advantages of 5 GHz’s free-and-clear spectrum. You lose
some speed when mixing A and N, but if you have the right set
of machines, it’s the best choice, unless you want to operate two
networks. (See Mix Legacy, New N Networks.)
• 802.11n only (5 GHz): The best choice for 5 GHz networks.
Additional options: If you hold down the Option key while
choosing from Radio Mode, you see four additional options:
802.11b only, 802.11b/g compatible, 802.11g only, and 802.11a.
These are provided in the interest of providing the most complete
support for older networking gear, I’ll wager.
The Channel pop-up menu lets you choose a channel based on the
band you selected. You are best off setting it to Automatic when you
use the 2.4 GHz band. The Automatic option is the only apparent
choice for 5 GHz. Choosing Automatic causes the base station to pick
the least occupied channel when the base station starts up or restarts,
but the base station doesn’t change the channel while running—only
after it has been restarted. To bypass Apple’s Automatic mode for
5 GHz channels, hold down the Option key as you pop up the Channel
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Warning! “Least occupied” (previous paragraph) means least
occupied by other Wi-Fi networks. In testing, even apparently
“empty” channels were sometimes full of interference from other
causes. While I couldn’t determine the cause, switching channels
alleviated problems, but it required choosing a channel rather
than relying on the Automatic setting.
Pick the Right Place for Your Base Station
When you walk around with a cell phone, the number of bars showing
signal strength varies with the quality of the signal that the phone
receives. These bars reflect the strength of signals received from
nearby cellular network transmitters on towers and roofs. It’s the
same issue 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 not penetrate with enough strength to be useful.
First, decide where you want service. Do you want to work in your
backyard? Upstairs and downstairs?
Second, think about the obstacles in the places you want to work.
Walls, ceiling, floors, and even metal exercise bikes can all absorb
and reflect Wi-Fi signals, reducing their range and quality.
While the Extreme N uses MIMO technology—multiple sets of
receiving and transmitting antennas—to cover a much greater area
than its predecessors, the base station still has its limits. It’s just
much closer to covering the area of a typical home than earlier units.
Pick a spot that is near the middle of where you want your signal to
reach and test to see if it’s a good location for your base station. 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 one spot to see if the signal strength
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• Use sticky notes to mark signal strengths at the locations where
you want to provide network access (see Testing from base station
to client, below). Also write down the current location of the base
station and the signal strength you’re seeing at that location so it’s
easy to sort out the ideal placement of the base station later.
TIP The AirPort menu lists networks alphabetically. Hold down the
Option key and select the menu, and Mac OS X re-orders the list by
signal strength, from strongest at the top to weakest at the bottom.
• When you move the base station, make sure to keep its orientation
the same. The antenna in a base station is omnidirectional—all
directions, but Apple designed the base station to have its strongest performance parallel to the horizon. It doesn’t come with a
mounting bracket, perhaps Apple’s way of emphasizing that you
should keep it in a horizontal orientation.
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 base station to client
AirPort Utility now incorporates what was a separate Apple utility
to monitor the performance of wireless adapters connected to a
base station.
To view this monitoring tool:
1. Launch AirPort Utility, connect to your base station, and choose
Base Station > Manual Setup.
2. At the top of the window, click the Advanced icon.
3. In the Advanced pane, on the Logging & SNMP view, click the Logs
and Statistics button (located near the bottom).
4. Click the Wireless Clients button.
You can now check the performance of any devices connected to
your base station (Figure 14). This nifty readout provides ongoing
monitoring of the signal rate for each connected device. Each device
is assigned a different color in the Client list beneath the graph, and
that color corresponds to a line that tracks signal strength over time.
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The graph at top shows the signal strength for each client. The bottom
lists each client by MAC address, with the actual measurements for
signal and noise, and the raw data rate.
The Client list shows connected devices by their unique adapter
number. (For more on adapter numbers, see What and Where Is a
MAC Address? on p. 59.)
For each client, the utility shows the signal and noise rates. The
signal-to-noise ratio is an absolute measure of potential throughput.
Signal and noise levels are measured in such a way that a negative
number means below a certain threshold, rather than an absence of a
signal or noise. Noise has a large absolute value, like -100; the larger
the absolute value, the less noise. The signal should be negative, too,
but have a lower absolute value, approaching 0; the closer to 0, the
better the signal.
NOTE The label dBm on the left of the graph means decibels below one
milliwatt (mW). Decibels are a logarithmic measure of power, and
dBm defines how much signal strength was received below the
nominal strength of 1 mW, a useful starting point for these kinds
of signals.
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The Rate column, however, has the most useful information: It shows
the raw data rate, in Mbps, at which the client is connected. This is
useful to know because you can have decent signal strength but be
connected at a lower speed than the raw 54 or 300 Mbps maximum
for 802.11g or 802.11n, respectively. The lower the connection speed,
the more likely you need to tweak the base station’s—or the
Testing from client to base station
The flip side when testing connections is measuring how strong
your base station is from the computer you’re trying to connect from.
iStumbler (http://www.istumbler.com/) is my detector of preference.
iStumbler provides a continuous scan with information about signal
and noise for all the networks in your vicinity (Figure 15).
iStumbler shows nearby networks. I made this scan in my office,
which is in the middle of a building in Seattle with a window off to
one side. Imagine a scan made in Manhattan.
If you’re truly frustrated with finding a good connection, you could
make an expensive purchase—or perhaps pool your dollars with
friends or colleagues—and get a spectrum analyzer. The Wi-Spy and
Wi-Spy 2.4x from MetaGeek run $199 and $399, respectively, and
provide a live analysis of the signals passing in the air around you.
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A spectrum analyzer constantly measures the strength of signals in
hunks of frequency, and produces an output that software can read
and display (Figure 16). The more energy or more spikes in a given
channel, the more likelihood that Wi-Fi won’t work there.
Wi-Spy and Wi-Spy 2.4x capture signal strength over time at
frequencies in the 2.4 GHz band and relay them to software like
EaKiu, which displays the results graphically. (Wi-Spy 2.4x data
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The next steps in setting up your AirPort network involve configuring
the LAN (local area network) and WAN (wide area network). For
many of us, this configuration is as simple as plugging in a couple of
cables—or maybe even one cable. But for more complicated networks,
a few more steps are involved to make sure the computers connecting
via the Extreme N can access the Internet, or the rest of a local
network, without you pulling out your hair.
More than one base station: If you’re building or re-building
a network with more than one base station, read this section first
for how to set up the base station that connects directly to your
broadband service provider. Then read Connect Multiple Base
Simplest Case: Plug and Go
Before getting into more exotic scenarios, let me give you the
rundown on the simplest possible case, which has two parts:
• You have a broadband cable or DSL modem that doesn’t require
any special login or restrictions in order to access the Internet.
(If you’re not sure, see Log in via PPPoE over broadband DSL
and Deal with MAC-address-restricted cable broadband.)
• You plan to share the Internet connection coming in from the
broadband connection among computers and devices that connect
to the Extreme N via Wi-Fi or Ethernet.
Here’s how to get your connection up and running:
1. Plug an Ethernet cable from the LAN port of your broadband
modem into the WAN port of the Extreme N.
2. Connect the computers on your network via Wi-Fi or Ethernet to
the Extreme N.
That’s it! This setup relies on the factory settings that an Extreme N
has when it’s first powered up. If this simplified setup appears to be
working, and you have no reason to think that it shouldn’t do the job,
then skip ahead to Connect Your Computers.
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If this simplified setup doesn’t work, or you know you have a more
complicated situation, read through the rest of this section to find
your scenario.
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 Extreme N into either a broadband
modem; or, if you have an existing Ethernet LAN to which you are
connecting the base station, into that larger network.
In either case, start with an Ethernet cable and plug the cable into
the Extreme N’s WAN port. Next, plug the other end into the LAN
port of your broadband modem, or into a port on an Ethernet switch
for a larger network.
Auto-sensing: Extreme N has auto-sensing, auto-switching
Ethernet, which means you can use either type of Ethernet cable—
straight-through or crossover—successfully. The Ethernet ports
also automatically adjust speed to the highest available rate.
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.
• A static address is more typical for small and large offices.
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 Extreme N
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 requests and provides an
address. And that’s as complex as it has to be.
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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; or a publicly
routable address, which is part of the global numbering system for
IP addresses.
The Extreme N is set to act as a DHCP Client if back in Step 7 of
Handle initial setup, you chose Using DHCP. No additional steps
should be needed (Figure 17).
The simplest way to get an Extreme N on the Internet.
In some limited cases, you might need to enter the DNS (Domain
Name Service) IP addresses manually. Your ISP should tell you those
addresses if you need them. DNS IP addresses are entered in the DNS
Server(s) fields (Figure 17, above).
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I recommend using OpenDNS to handle your DNS resolution
instead of DNS server information provided by an ISP. OpenDNS
has a few neat features that improve on normal DNS resolution.
First, they’re much faster than most ISPs, making the Web seem
snappier. Second, they can fix typos, for instance, when you enter
an address that doesn’t exist—flickr.cmo becomes flickr.com.
Third, they offer a custom account that lets you set DNS shortcuts
so that when you type a word into a browser’s Location field, you
control what domain name is looked up.
See http://www.opendns.com/ for more details, including their two
nameservers’ IP addresses.
Some ISPs require you to jump through additional hoops to connect
to their networks: a login process or a way to restrict access to a single
computer. The former is used mostly by DSL providers; the latter, by
cable firms.
Log in via PPPoE over broadband DSL
For security and tracking purposes, many DSL providers require
you to use a technology called PPPoE (PPP over Ethernet) when
connecting to their network. With PPPoE, you log in with a user name
and password to your ISP over your DSL connection, at which time
you are automatically assigned an address and the connection works
just like any other broadband connection.
If you need PPPoE, configure it in the Internet pane of AirPort Utility
in the Internet Connection and PPPoE views (Figure 18). The base
station connects per the setting you choose in the Connection pop-up
menu in the PPPoE view: Always On is the most likely choice.
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PPP over
using a login
name and
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
(see What and Where Is a MAC Address? next page). ISPs use two
common methods for restricting access by MAC address:
• In the less annoying method, the cable modem powers up and
locks on to the MAC address of the device connected to it. You can
switch between devices by unplugging and reconnecting the cable
modem after you connect your Extreme N.
• In the more annoying method, you register the MAC address with
the ISP manually or through an automatic process. You may need
to call your cable provider—which may want to charge an additional monthly fee—to register the MAC address of your Extreme
N’s WAN port. (The WAN port’s MAC address is printed on the
underside of the Extreme N, as the Ethernet ID.)
Warning! A feature in non-Apple Wi-Fi gateways, called MAC cloning or spoofing, lets you enter any MAC address for the WAN port. No
AirPort base station firmware version has this common feature.
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The MAC, or Media Access Control, address is a unique, factoryassigned address for every network device, including Ethernet and
Wi-Fi adapters. 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; Apple
has at least two common ranges, which begin with 00:0a:95
and 00:03:93. MAC addresses are frequently used for filtering,
authentication, and WDS, often without requiring direct entry.
Here’s how to find MAC addresses for Apple’s devices:
• Extreme N: Look on the bottom of the base station to find
the MAC addresses of the WAN Ethernet port and the Wi-Fi
adapter. Or, in AirPort Utility, select a base station at the left
to see its MAC addresses on the right:
◊ The AirPort ID is the device’s wireless MAC address.
The Ethernet ID is the WAN port’s MAC address.
• Computers connected to an Extreme N: In AirPort
Utility, select the base station and choose Base Station >
Manual Setup. Click the Advanced icon, and then—on
the Logging and SNMP view—click the Logs and Statistics
button. Click the DHCP Client button and a list of MAC
addresses appears. You can turn your computer’s Wi-Fi
adapter off and on to see which MAC address corresponds
to your computer.
• Wi-Fi adapter in a Mac: In Mac OS X, open the Network
preference pane in System Preferences and choose AirPort
from the Show pop-up menu. The MAC number is listed as the
AirPort ID. (Ethernet MAC addresses are labeled as Ethernet
ID in the Ethernet view.)
• Wi-Fi adapter under Windows: In Windows XP or Vista,
view the connection status of the adapter and click Details
below the Connection Status section. The Physical Address is
the MAC address.
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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 in which 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 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 or servers: You need 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 enter these values, click the Internet icon at the top of the AirPort
Utility window; click the Internet Connection button, and choose
Manually from the Configure IPv4 pop-up menu (Figure 19).
the Internet
manually by
entering the
static values
provided by
your ISP or
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The other element of mystery in setting an IP address is what,
exactly, is IPv4? IP stands for Internet Protocol, but v4 means
“version 4,” the form of IP used in Internet networking for decades.
That distinction has become important with the availability of IPv6
(version 6), which Apple supports in Mac OS X and Extreme N,
among other products. IPv6 isn’t widely available, but it is out there
and will become increasingly embedded in our lives and devices.
See IPv6 settings for more details.
Hand Out LAN Addresses
With the WAN configured, 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 Extreme N
shares one incoming Internet address with all the machines on
LAN. The base station assigns addresses to computers on the LAN
from a private range; you can modify what that range is. The
addresses are typically transient for any given computer. The
Extreme N 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 Extreme N shares
multiple, publicly routable Internet addresses with computers 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 an Extreme N to let
another device on a larger network dynamically assign addresses
or allow static addresses. With this set up, the Extreme N doesn’t
manage addressing.
The first option is by far the most common, in which computers on
the LAN receive addresses that can change from time to time, and
which exist solely to give the computers access to the Internet. The
other options are typically used when computers on the LAN side of
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the network need to be reached by computers on the Internet or by
computers on another LAN to which your Extreme N is connected.
Let’s look through each of these in turn.
Warning! In testing the Extreme N, I discovered performance
issues in one particular configuration. A NAT-enabled Extreme N
bogs down when you send data between devices on the base
station’s LAN (via Ethernet or Wi-Fi) and devices on a network
connected to the base station’s WAN. In this rare configuration,
Ethernet tops out at 70 Mbps; Wi-Fi at 50 Mbps. Fortunately, you
would almost never use NAT on a base station that connects its
WAN port to an office or a larger LAN network—see Passthrough
and Bridging.
Apple is aware of this problem (I reported it), and they improved
the speed by 25 percent from the Extreme N (original) to Extreme
N (gigabit) model.
NOTE DHCP works by having a computer or other device send out 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 don’t need to proceed further in
this section to set up the base station; you can skip ahead to the
next section, Connect Your Computers.
However, should you want to control which addresses are assigned
or manage other details of NAT and DHCP, read on.
Set up the base station
In AirPort Utility, click the Internet icon at the top of the window,
click the Internet Connection button, and choose Share a Public IP
Address from the Connection Sharing pop-up menu.
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Set up client computers
With an Extreme N set to use dynamic addressing, each of your
computers needs to be set to receive an address via DHCP. This is
the default setting for any network adapter.
In Mac OS X:
1. Open the Network preference pane.
2. Switch to the TCP/IP view for any adapter—Wi-Fi or Ethernet.
3. Choose Using DHCP from the Configure IPv4 pop-up menu
(Figure 20).
set to use
OS X automatically obtains
a dynamically
assigned IP
address, in this
case from a
private range.
Your Mac should now be set up to receive an IP address via DHCP.
In Windows XP and Vista:
1. Choose Control Panel from the Windows menu.
2. Access network connections:
• In XP, open Network Connections.
• In Vista, open the Network and Sharing Center, and then in
the left-hand Tasks list, click Manage Network Connections.
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3. Right-click the adapter you want to view settings for, such as
Wireless Network Connection, and select Properties. (In Vista, you
should be prompted to approve that action; click Continue, if so.)
4. In the Networking tab that appears, select Internet Protocol
(TCP/IP) in XP or Internet Protocol Version 4 (TCP/IPv4) in Vista,
and click Properties. TCP/IP settings are configured in the General
tab; the default settings are the correct ones (Figure 21).
In Windows Vista,
selecting Obtain an IP
Address Automatically—
the default setting for
an adapter—allows the
operating system to get
a dynamic address.
(In Windows XP, the
interface for making
this selection looks
quite similar.)
Your Windows system should now be configured to receive an IP
address via DHCP.
Refining base station DHCP settings
You have two additional views in the Internet pane in AirPort Utility
for configuring the LAN. These allow you to control how private
addresses are generated.
The DHCP view offers a DHCP Range pop-up menu where you
choose one of three reserved ranges of private addresses—10.0.*.*,
192.168.*.*, or 172.16.*.*—as the two-number prefix to your private
network numbers. (The prefixes in the pop-up menu are reserved by
the global numbering authority, and they are guaranteed to not be in
use on any public Internet network.)
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You enter the third number, any number from 1 to 254, in the field
to the right of the pop-up menu. The fourth number is generated by
DHCP in a range limited to the starting and ending values shown in
the DHCP Beginning and Ending Address fields.
The only reason to change the range of numbers is if you want to
create and assign static private addresses. These would be addresses
that start with the first three numbers in the base station’s private
network range, but which you enter 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; see
Reserved addresses, next page.
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.
Limited addresses: The range you assign must start with the
same prefix you defined in the DHCP Range pop-up menu. AirPort
Utility prevents you from modifying the first three numbers in the
four-number IP address in the range fields. This is also true
anywhere you can enter a LAN address in AirPort Utility.
In the DHCP view, you can also 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, and you can set the DHCP Message, which
will pop up in a dialog box on a computer when the computer receives
its DHCP address. (The LDAP Server field is relevant only for networks that use that directory protocol.)
The DHCP Reservations list is in Reserved addresses (next page).
Also on the Internet pane, the NAT (Network Address Translation)
view has 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.
Dynamic public addresses
Some people need to assign public addresses to their LAN computers
so that each computer can be reachable from the Internet. In this
case, you usually want to use a static public address, in which you
must configure each computer manually, and DHCP isn’t involved.
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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 an Extreme N to hand out
public addresses from a defined range using DHCP.
To configure an Extreme N to assign dynamic public address, follow
these steps:
1. In AirPort Utility, select the base station at the left, and then click
the Internet icon at the top of the window.
2. Now, on the Internet Connection view, from the Connection
Sharing pop-up menu, choose Distribute a Range of IP Addresses.
In this mode, the NAT button disappears because there’s no
translation going on.
3. In the DHCP view, enter values for DHCP Beginning and Ending
Address. The range you specify is limited to the same IP network
that the Extreme N uses for its Internet Connection IP address. For
instance, if your Extreme N is, your range has to be
within and
Warning! Using public routable addresses means your entire
base station LAN is fully exposed to the higher-level network
through its WAN port, which usually means that all the computers
can be reached via the Internet.
Reserved addresses
Reserving an IP address using DHCP is a new feature in the Extreme
N—new to Apple, as it’s been available in other devices for years.
Reservation allows a given computer 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 Extreme’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 has to restart or is shut down, the next time
the computer powers up and its network adapter is active, that computer still receives its reserved address.
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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 a reserved address:
1. In AirPort Utility, in the DHCP view of the Internet pane, click the
The DHCP Reservation Setup Assistant (Figure 22) appears.
The assistant
lets you set
up a reserved
DHCP address
by MAC
address or by
DHCP client ID.
2. Enter a description, which will later appear in the DHCP
Reservations list.
3. Select whether to reserve an IP address by a Wi-Fi adapter’s MAC
address or by its DHCP Client ID, and click Continue. DHCP Client
ID is easier to set up, but works only with Mac OS X (and earlier).
4. Now:
• If you reserved by MAC address: enter the MAC address
(AirPort Utility fills in the colons as you type two-digit hexadecimal numbers), choose the last number in the IP range that
you want to reserve, and click Done (Figure 23). If you need
help locating the MAC address, see What and Where Is a MAC
Address? (p. 59).
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Enter the MAC
address and
your reserved IP
address, and then
click Done.
• If you selected Reserve by DHCP Client ID: The DHCP
Client ID is a text tag that you assign when configuring a Wi-Fi or
Ethernet adapter. This text is transmitted when an adapter requests
a dynamic address (Windows XP and Vista don’t support this),
and the base station uses that tag to assign a reserved IP address:
a. First set the DHCP Client ID on a client computer running Mac
OS X: Open the Network preference pane, click TCP/IP, choose
Using DHCP from the Configure IPv4 pop-up menu, and enter
the DHCP Client ID in the field at the right. Figure 24 shows
the DHCP Client ID set to GlennDualMac.
The DHCP Client ID
field is found in the
TCP/IP view when
the Configure IPv4
pop-up menu is set
to Using DHCP.
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Warning! To avoid confusing the Extreme N, make sure that
DHCP Client IDs are unique.
b. In AirPort Utility, enter that DHCP Client ID in the DHCP
Reservation Setup Assistant and click Done (Figure 25).
Enter the same
DHCP Client ID in
AirPort Utility.
5. When you’ve entered all the reservations, click Update.
After restarting, the DHCP Reservations list shows the entries you
made and any computers listed will have retrieved their new addresses.
Passthrough and bridging
For networks in which the Extreme N 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:
1. In AirPort Utility, click the Internet icon at the top of the window.
2. In the Internet Connection view, choose Off (Bridge Mode)
from the Connection Sharing menu. The DHCP and NAT buttons
disappear in the Internet pane when that option is selected.
3. Click Update to restart the base station.
With bridge mode, the Extreme N simply passes through any DHCP
messages or other traffic, and isn’t involved in assigning addresses.
NOTE If you connect base stations wirelessly using Wireless Distribution
System, all the base stations other than the “main” unit, which acts
as the Internet or LAN conduit, are turned into bridges. See Bridge
Wirelessly for details on setting up a WDS connection.
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Once you’ve set up your Wi-Fi network and connected it to the
Internet, you’ll want to configure your computers to connect to
the network properly, whether you’re working with a few desktop
computers or helping customers use a public hotspot. Making a
connection is quite simple, but configuring how your computers
connect may take a little thought. You might choose to connect
automatically to unknown networks, or need to connect to a network
that doesn’t advertise its name. You may also reconnect to networks
that you’ve visited before.
Read this section to learn how to use Tiger (below), Windows XP,
and Windows Vista to connect to networks, modify stored profiles for
networks, and choose when to connect to unknown networks.
NOTE Leopard hasn’t shipped as the book goes into production. To learn
about the Leopard update to this book, click Check for Updates on
the cover and sign up for the update mailing list. If you have only
the printed version of the book, send us an email message.
Warning! Remember that if you set up your network as 802.11nonly in the 2.4 GHz band, or if you set the base station to use the
5 GHz band, neither an 802.11b nor a 802.11g adapter found in an
older computer will be able to connect. If you can’t see your network
on a given computer or can’t connect to a network that shows up
in a list of available networks, check your base station setup (see
Consider your spectrum choices for more details).
Connection problems: 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 Tiger
Connecting to a Wi-Fi network with Mac OS X involves two phases:
discovering, or finding, a network, and connecting to it. Separately,
you can create stored profiles for Wi-Fi networks that you wish to
connect with automatically in the future.
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Warning! If the AirPort status menu on your menu bar displays
an icon like an open fan (shown at left), your network adapter is
turned off. To turn it on, choose Turn AirPort On from the menu.
If the AirPort icon still looks like a fan or you get an error saying
that there’s no card or it can’t be turned on, you may have a
hardware problem. If you have a model with a removable Wi-Fi
card, check that the car is seated properly: power the computer
down, open the case, and check the card; start up the machine
and see if AirPort is now available. If you don’t have a serviceable
card or this doesn’t help, bring the computer in for service.
Mac OS X constantly looks for networks when the Wi-Fi adapter is
turned on, and a list of them appears in the AirPort status menu at
the right of the menu bar (If you don’t see the menu, you can turn it
on by opening Internet Connect from /Applications. A checkbox
for the menu is on the AirPort pane.)
You can also use software like iStumbler to get more information
about your own and other networks in the vicinity (see Testing from
client to base station).
If a Wi-Fi network appears in your vicinity and you aren’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), Mac OS X alerts you
(Figure 26). From that alert, you can then choose whether you wish
to connect to the network, and if you want Mac OS X to remember the
network so that you always connect to it again in the future.
Mac OS X
alerts you to
a new network
and lets you
choose to
always join it
in the future.
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You can configure a Mac running Tiger so that it automatically
picks which network it connects to: Mac OS X can recognize a new
connection when you wake up or turn on the Mac, when you turn
AirPort off and back on, when a network is turned on near you, or
even when a Wi-Fi network disappears and reappears while you’re
actively using your computer.
Warning! The fact that Mac OS X and other operating systems
constantly scan for networks is a security problem. Many patches
were released in 2006 that dealt with flaws in Wi-Fi drivers that
could be exploited with maliciously crafted data designed to crash
an operating system when it is scanning for networks. This is one
reason why it’s critical to keep your software up to date, especially if you use Wi-Fi networks that aren’t in your home or office.
To connect to a network, you typically select its name from a list,
and then enter an encryption key if it is secured. In some cases, you
might have set up your network to be “closed” (invisible to casual
passers-by). Let’s walk through these options for connecting.
Connect to a named network
To connect to an AirPort network in Tiger when the network broadcasts its name—as most do—choose the network name from the
AirPort status menu (Figure 27). The AirPort menu’s icon should
go from gray to black, with the number of black waves indicating
signal strength by their quantity.
Choose a network from the list or choose
Other to join a closed network by name.
At hotspot networks and other open networks, before you can do
anything else on your connection, you may need to open a Web
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browser window and try to visit any site. Instead of going to that site,
the network will redirect you to a gateway page at which you may be
asked to agree to terms of service, or enter account information or a
credit card number to proceed. You typically have no Internet access
until you’ve passed the gateway page.
If the network is secured with a key, see just below for the next steps,
or look on the next page for WPS information.
Enter an encryption key (WEP, WPA/WPA2 Personal)
If encryption is active on the network, after you select the network
name, you are prompted by a dialog to enter an encryption key.
Typically, the AirPort software on a Mac automatically chooses the
correct encryption type, and you simply enter the encryption key that
you have been given or that you set yourself for the network.
Save the key, save time: You can choose to store the key in the
Keychain to avoid having to retype it in the future.
If the encryption type is incorrect, you can choose the correct type
from the pop-up menu. Click OK to join the network.
You enter an encryption key or passphrase differently depending on
how the network was configured. Extreme N networks can always be
joined with either a WPA or a WPA2 password, but WEP keys may be
needed to join older networks:
• Apple WEP Password: If you created a WEP key on an original
AirPort Base Station, the 2003 Extreme, or an AirPort Express,
enter the password exactly as you entered it in setting up the base
station or as it was provided to you.
• WEP hexadecimal key: If you are joining a non-AirPort
network, you need to enter a $ (the dollar sign character) followed
by 10 to 26 hexadecimals digits. Whoever set up that network
needs to provide those hex numbers to you.
• WEP ASCII key: If the network was set up with WEP using an
ASCII (text) key, you must enter that password between quotation
marks, like "fishy". WEP ASCII keys are 5 or 13 characters long.
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Extract WEP key: AirPort Utility lets you extract a WEP key
when using WEP Transitional in case you have older Windows
computers or other devices that need to join. Connect via the
utility to your base station, choose Base Station > Manual Setup,
and then choose Base Station > Equivalent Network Password.
The ASCII and hex WEP keys are identical, just expressed in
different forms.
• WPA/WPA2 passphrase: Enter the passphrase exactly as it
was entered on the Extreme N or other base station. All computers
handle WPA/WPA2 passphrases the same way. Some networks
may be configured to accept either a WPA or a WPA2 password;
others may require only a WPA2 password.
Warning! Macs with the original AirPort Card cannot connect
to WPA2 Personal protected networks, but won’t provide an error
to explain that. If you are using an AirPort Card on an older
machine, make sure via AirPort Utility that the network is
configured with WPA/WPA2 Personal, not WPA2 Personal.
• WPA/WPA2 hex key: In rare cases with WPA or WPA2, you
may need to enter the 64-digit hexadecimal encryption key. To
enter this in Tiger, hold down the Option key while selecting WPA
Personal or WPA2 Personal from the Wireless Security pop-up
menu, and an extra large field appears allowing entry. Yes, it’s a
pain to enter 64 hex digits.
Connect to a simplified secured network with WPS
Wi-Fi Protected Setup (WPS) lets you join a secured network without
entering an encryption key. But this method requires access to the
base station via AirPort Utility at the time you want a computer to
join the network. To read the full procedure, skip ahead to Use WPS.
Connect to a closed (hidden) network
For a closed network, choose Other from the AirPort status menu. In
the resulting dialog, enter the network’s precise name (close doesn’t
count), and choose the form of encryption and enter the password.
If there’s no encryption, leave the option set to WEP Password and
enter no password. Click OK to join. (For more on closed networks,
see Closed network.)
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Saved locations
Tiger can automatically connect to networks that you’ve joined
previously, including password-protected networks for which you’ve
saved the password in your Keychain.
But you can also create custom settings for different locations where
a computer might be used (perhaps at the office, at a relative’s house,
and at a local coffee shop), and you can set up multiple profiles at
each location.
To create a new location, in the Network preference pane, choose
New Location from the Location pop-up menu, enter a name, and
click OK.
Managing profiles
You can manage profiles for connected networks and create new
profiles from scratch. To show those profiles, and to create and edit
1. In the Network preference pane, choose your AirPort adapter from
the Show pop-up menu and click the AirPort button.
2. Choose Preferred Networks from the By Default, Join pop-up menu.
A list of networks appears, ordered from top to bottom by the most
preferred to least preferred network to join.
Warning! Even though you can create different profiles for your
other network settings through the Location pop-up menu, Wi-Fi
networks in this profiles list are shared in all locations.
Warning! I discovered a bug some time ago with location profiles
created in Panther and used in Tiger. I was unable to get Preferred
Networks to appear in the pop-up menu with a Panther-created
location; instead an option that’s not supposed to appear in Tiger
shows up: A Specific Network! When I created a new location in
Tiger, the correct menu commands appeared. This bug has never
been fixed.
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3. To work with these profiles:
• Add a profile manually by clicking the
• Delete a profile you no longer need by selecting the profile and
clicking the
• To edit an existing profile, select it and click Edit; you can
change the password or type of password, too.
• To change the preferred order in which the Mac connects to
networks if more than one is available, drag a network name
to a new position in the list.
4. Click Apply Now when you’re done.
Advanced connection options
For more control over how a Mac connects via AirPort at a particular
location, in the Network preference pane, choose a location, click the
AirPort button, and then click Options at the lower left. Now you can:
• Set whether you want to add profiles for new networks that you
connect to by checking or unchecking the “Automatically add new
networks to the…” box. (If, instead, you chose Automatic from the
By Default, Join pop-up menu, that box is checked and cannot be
disabled. In Automatic mode, you manage networks entirely via
the AirPort status menu.)
• You can also choose one of three items from the If No Preferred
Networks Are Found pop-up menu:
Ask Before Joining an Open Network lets you join any network
that’s within your Mac’s range, but first prompts you.
Automatically Join an Open Network is ill advised: it’s rare that
every open network will be acceptable to you, or even intended
for use by outsiders.
Keep Looking for Recent Networks prevents your Mac from
joining, or asking to join, networks that you haven’t agreed to
connect to before.
• In Tiger, Apple added the checkbox Disconnect from Wireless
Networks When I Log Out, which disconnects the Mac when no
user is active. This makes sense for users who routinely log out
of Mac OS X, or on computers with multiple users.
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TIP If you can’t get your AirPort interface to connect to a network, Tiger
has a troubleshooting feature called Network Diagnostics that’s
available when you click Assist Me at the bottom of the Network
preference pane.
When you enter a WEP, WPA, or other encryption key in Mac OS X,
it’s stored in the Keychain. You can run Keychain Access (located 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 Mac OS X user
password, unless you specifically set a special Keychain password,
which you can do in Keychain by choosing Edit > Change Password
for Keychain “keychain name”. For more advice on Keychain, see
Take Control of Passwords in Mac OS X.
Connect in Windows XP
In this subsection, I first look at how to make a basic connection. I
then cover a few more advanced options, and look at how to create a
preferred network profile. In all cases, my steps apply specifically to
Windows XP Service Pack 2 (SP2).
Discovery and connecting
To start setting up a Windows computer to connect to a wireless
network under Windows XP Service Pack 2, right-click the wireless
network icon in the System Tray and choose View Available Wireless
Windows responds by showing any networks that it can see, along
with info about the status and nature of each one (Figure 28). This
is an enormous improvement in SP2 over previous XP releases, which
left you guessing.
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If Windows XP says that another program is controlling wireless
access or that it can’t use the wireless adapter, Wireless Zero
Configuration may be at fault. Despite its name, it needs handholding: Go to Control Panels, open Administrative Tools, then
open Services, and finally select Wireless Zero Configuration. Click
the square stop button at the top of the Services window; after
you’ve been told that the service has stopped, click the triangular
start button.
That typically takes care of the problem.
Windows shows you all the networks that it can see in the vicinity,
as well as their security parameters and signal strength.
Now, select a desired network and click Connect, at which point
you’re prompted for any encryption keys needed to join.
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Advanced connection options
Now that you’ve established a connection, you can tweak aspects of
that connection. To see more options, at the left, in the Related Tasks
list, click Change the Order of Preferred Networks. That brings up
the Wireless Networks tab of the Wireless Network Connection
Properties dialog (Figure 29).
You can use this tab
for many tasks, such as
setting which networks
you prefer to connect to
in which order when more
than one is available (use
the Move Up and Move
Down buttons).
symbol at the top
of the Preferred networks
list marks the currently
connected network.
A red x ( ) marks any
networks that are not
An icon by itself ( )
means the network is
available in the vicinity.
This dialog box is a bit of a powerhouse despite its demure
appearance. Using it as a launching pad, you can:
• Re-order your preference for which network your machine
automatically connects to. Select a network name and click
the Move Up or Move Down button to rearrange it.
• Add new Wi-Fi connections. Click Add.
• Delete a preferred network. Select a network and click Remove.
Your computer no longer automatically joins that network.
• Set advanced connection properties: Click the Advanced button
and then choose whether to connect to any available network,
only to base station Wi-Fi networks (access point or infrastructure
Page 79
networks), or only to ad hoc (computer-to-computer) networks
(Figure 30). You can also choose whether to connect automatically to non-preferred networks—ones that you haven’t already
set up profiles for. I recommend leaving that box unchecked.
The Advanced dialog
box controls how your
computer connects to
available networks that
it finds.
Creating a preferred network profile (WPA/WPA2)
To set up a stored preferred network profile with WPA/WPA2, follow
these steps:
(I don’t describe how to use WEP encryption here because you are
unlikely to be limited to WEP on a Windows XP SP2 system when
connecting to an Extreme N!)
1. Navigate to the Wireless Networks tab for a Wi-Fi adapter as
shown in Figure 29 (previous page).
2. Now, either:
• Add a new profile by clicking Add.
• Select an existing profile, and click Properties.
3. If you don’t already have one filled in, enter the network name
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4. Set network authentication to WPA-PSK, and set data encryption
to TKIP for WPA, or to AES for WPA2 (Figure 31).
Choose WPA-PSK and
TKIP in order to enter
your WPA key; choose
AES from the Data
Encryption pop-up
menu for WPA2.
5. Enter your WPA or WPA2 passphrase in Network Key and again
in Confirm Network Key. Since you can’t see the key as you type it,
you can’t verify visually that you have typed it correctly. Retyping
the key helps ensure that you’ve entered it correctly.
6. Click OK.
Windows stores the profile. You can then drag the profile to make it
more or less preferred than other networks already listed.
Connect in Windows Vista
Windows Vista streamlines connecting to a Wi-Fi network by providing much clearer information than Windows XP’s process along
with a better designed interface for working with wireless networks.
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Warning! Because Draft N is in flux, a Windows computer with
an 802.11n adapter might have trouble making a connection to
the Extreme N. In testing, I found I couldn’t get the highest speed
connection rates using an Intel Draft N card that had been released
at the same time as Apple’s N enabler and Extreme N (original).
Firmware updates due in late 2007 should improve this situation
To see what Wi-Fi networks are available in Vista, right-click the
Network icon in the System Tray and select Network and Sharing
Center. Click Connect to a Network from the left-hand Tasks list.
This reveals a list of wireless networks (Figure 32). If you hover
the pointer over a network, more detail is revealed, such as the type
of network encryption.
View available
Let’s connect to a Wi-Fi network with Vista. You can double click
a network in the browser shown above in Figure 32, or select a
network and click the Connect button to start:
• Open network: If the network is open, Vista warns you that
there’s no protection with an exclamation point in a shield.
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• Secure network: A secure network appears in the list as
a “Security-enabled network,” and when you select it and click
Connect, Vista prompts you for an encryption password
(Figure 33). Unlike in XP, you need only enter the key once—
I mean, if it’s wrong, it’s going to tell you, right? Vista, like Mac
OS X, handles the password type automatically, but doesn’t tell
you what kind of encryption is being used. You can also select
the Display Characters checkbox to see what you’re typing.
Enter the
security key
to connect to
the network.
Next, Vista shows a dialog while it’s trying to connect, and even
warns you if the connection is taking longer than usual to hook up
(Figure 34).
The progress
bar shows
that something is
while the
is set up.
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Managing profiles
Vista offers a new profile manager to help store information about
networks you’ll connect to on an ongoing basis. In the Networking
and Sharing Center, click Manage Wireless Networks in the left-hand
Tasks list. The resulting dialog is shown in Figure 35.
You can add
and configure
networks that
you connect
to regularly in
Vista’s profile
To add a profile, follow these steps:
1. Click the Add button.
2. Make one of the following choices:
• Choose Add a Network That is in Range of This Computer
(scan for networks).
Now enter an encryption key when prompted. Vista will store
the key along with your other network details.
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• Choose Manually Create a Network Profile (enter the network
Now, you can enter your network’s name, encryption type, and
security key (Figure 36):
For WPA, choose WPA-Personal from the Security Type popup menu, and TKIP from the Encryption Type pop-up menu.
For WPA2, choose WPA2-Personal from the Security Type
pop-up menu and either TKIP or AES from the Encryption
Type pop-up menu.
Set up a
manual profile
for a network
you connect
to more than
3. Click Next and then Close.
The profile appears in the networks list.
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Wi-Fi is described as reaching “only” about 150 feet, which is a very
rough estimate of the radius of older 802.11b and g devices. With an
Extreme N, the distance is much farther. But you can also extend the
covered area by adding more base stations with overlapping signals.
As a Wi-Fi adapter in a laptop or handheld moves across overlapping
areas, it can automatically switch base stations while maintaining
a continuous network connection—as long as you’ve set the network
up right.
While it’s always critical to follow instructions exactly when setting
up any kind of network gear—or almost anything computer related—
extending a network with more base stations is particularly rough
because a failure to check one box or enter exactly the right text could
result in a network problem that none of the base stations can
accurately report.
If, in following the steps below, you find yourself stymied, retrace
your steps from the start and see what went wrong.
When you extend a network, the additional base stations tend to
be dumb; that is, they don’t assign out addresses or handle other
features you think of as belonging to a base station’s set of options.
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 typically called access
points to distinguish them from routers.
Because dumb base stations (access points) simply pass traffic
through, an adapter retains the same IP address as it switches from
one base station to another, thus maintaining a continuous connection in most cases.
There are two mix-and-match methods of extending your network:
• Add base stations via Ethernet
• Add base stations wirelessly via Wireless Distribution System
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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 extending a network via Ethernet.
Add Access Points via Ethernet
When you add access points, 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.
Different names for seamless networks: In Mix Legacy, New
N Networks, I will advise you to set different network names for
the old and new networks. That advice is designed to keep the
networks separate. However, when adding access points to grow
a single network, you keep the same name so that the connecting
computers see the network as a single entity.
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 37). However, you can also use wireless connections or
electrical connections to form that network backbone, as I describe
ahead in Bridge Wirelessly and Extend with HomePlug.
A common
connects one
base station
in the living
room, another
upstairs, and
a third in the
Page 87
The most important part of adding access points is choosing the
Wi-Fi channels for them wisely. Because each access point can communicate over a unique hunk of spectrum, you can avoid interference
by making sure that no adjacent APs use the same frequencies. See
Configure the Spectrum and Channel for more details on how to pick
channels. Typically, all the base stations on an extended network will
use either the 2.4 GHz or 5 GHz band for simplicity, but it’s not
strictly necessary (see Mix Legacy, New N Networks).
Set up a main wired base station
Your main base station should be plugged into your broadband connection, and configured as discussed in Set Up Your Network for
setting up a base station to share addresses.
Where you deviate from those instructions is in choosing the channel
for the base station to operate on. You need to select the 2.4 GHz or
5 GHz channel manually, rather than using the Automatic setting, so
that you can set additional base stations that overlap to use different
channels. Instead of following the procedure detailed in Set a band
and channel, follow these steps:
1. Launch AirPort Utility, connect to your base station, and choose
Base Station > Manual Setup.
2. In the AirPort pane’s Wireless view, choose a numbered channel
from the Channel pop-up menu.
• If you chose from the Radio Mode pop-up menu either “802.11n
(802.11b/g compatible)” or “802.11n only (2.4 GHz),” select
channel 1, 6, or 11. These are the “clearest” channels that can be
used in overlapping areas.
• If you chose from the Radio Mode pop-up menu either “802.11n
(802.11a compatible)” or “802.11n only (5 GHz),” hold down the
Option key to select a 5 GHz channel manually, such as 36.
3. Click Update to restart the base station with these changes.
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Set up additional wired base stations
Adding additional access points is straightforward:
1. Launch AirPort Utility, connect to your base station, and choose
Base Station > Manual Setup.
2. In the AirPort pane, choose the Wireless view.
3. Enter the same Network Name as your main base station (this
enables seamless roaming).
4. Choose a channel that won’t interfere with your main base station
or other base station’s choices:
• In 2.4 GHz (B, G, or N), any three base stations can uniquely
use channels 1, 6, and 11 with the least interference. If you set
your main to 1, set an additional one to 6, for instance.
• In 5 GHz (A or N), all channels are nonoverlapping. But if you
use the “wide” channel mode, an Extreme N 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.
5. Choose the same Wireless Security option and enter the same
Wireless Password as on your main base station.
6. Click Update to restart your base station with the new settings.
7. Plug your 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.
Page 89
What’s the most robust and ubiquitous wired network in your
home? The electrical system! We don’t think of data transmitting
over power, but all wired networks use electricity to encode data.
In the case of powerline networking, small adapters plugged into
outlets modulate data over the 60-hertz (Hz) frequency used in
U.S. power. At least three incompatible versions of powerline
networking now exist, operating at speeds up to 200 Mbps.
Powerline networks have no central hub in most cases. Mac users
should purchase Ethernet bridges, which offer a single Ethernet
jack. You plug a cable from a Mac into this bridge, plug the bridge
into a wall socket, and you’re done. The powerline system
handles communication among all the adapters on your electrical
When I say “wall socket,” I do mean wall socket: powerline networking typically cannot work when an adapter is plugged into a
power strip.
To extend a wireless network, simply place your access points
in appropriate locations, configure them as described above for
Ethernet network extension, and then plug them into HomePlug
Ethernet bridges (Figure 38). And that’s it.
A powerline
works like
Ethernet over
Page 90
Bridge Wirelessly
Wireless Distribution Service (WDS) is a neat way to extend an
AirPort network without running wires between locations. As I noted
previously, 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.
TIP 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 both 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
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 39).
NOTE The biggest downside in WDS is that on a busy network, you
effectively halve, quarter, or even eighth, your available bandwidth:
All the network traffic that travels among access points over WDS
reduces the overall throughput of the network. But with an effective
network throughput of nearly 100 Mbps on an 802.11n network, even
splitting that into pieces still provides plenty of usable bandwidth.
Page 91
The same
basic setup for
an Ethernetconnected
network can
work with
Here, each
base station
is set to WDS
and also to
serve access
to local
Distribute wirelessly
In general, to set up WDS you need to know the MAC address for each
of the wireless gateways you want to connect (see What and Where Is
a MAC Address?, earlier, p. 59).
Mix and match: You can mix and match an older or newer
Extreme and the AirPort Express, as long as you recall that the
802.11g devices slow down overall network performance both by
the general backward compatibility overhead hit (about 10 percent
loss there), and when they’re actively sending or receiving.
Resolved bug—Extremes didn’t mix: In testing for this first
edition of the book, I found WDS would not work between an
Extreme N (original) and an Extreme 2003. When I tested the
Extreme N (gigabit), I had no such troubles.
Apple requires that you configure one device as the main base
station; you should choose the one best positioned to connect to
an Internet feed. Base stations that connect to the main are called
remotes, and they relay traffic via the main to and from their clients,
whether to other clients on the local network or the Internet. Finally,
Apple defined a relay, which a remote can connect to and which is
in turn connected to a main. Relays can’t connect to relays; remotes
can’t connect to remotes. You could have 4 remotes on each relay
Page 92
and 4 relays connected to a main for a total of 21 base stations
(Figure 40), although bandwidth would be enormously reduced.
If one main
base station
tells four
friends, and
they tell four
friends… well,
this is what
In a wireless network in which more than two access points
connect among themselves in any manner, the “hidden node”
problem occurs when one node has at least two access points that
can see the node but can’t see each other. Wi-Fi relies on collision
detection that requires that every device on a segment can spot
when other devices start transmitting and then back off.
With a hidden node, some devices can’t tell when other devices
are transmitting, resulting in crosstalk, interference, and other
problems. When designing a network to use WDS with more than
a few access points, you may have to give this issue some consideration, keeping all base stations within at least weak reception
range of each other. In some cases, you’ll experience reduced
performance if you ignore it; in others, the network might
mysteriously vary in its quality and reliability.
To set up a WDS network, follow these steps, repeating for each base
station you need to configure. There are two separate methods: one
for all-Extreme-N networks (next page); another for a Mix of Extreme
N and older Extreme/Express units, ahead.
Page 93
All Extreme N
Apple rather oddly added a way for Extreme-N base stations to
configure themselves via WDS without providing enough cues for
most of us—myself included—to figure it out. You have to read
page 46 of their ebook on designing 802.11n networks to find this out!
And even then, it’s a bit obscure. (See Designing AirPort Networks
Using AirPort Utility, a free download from http://www.apple.com/
Warning! This option works only with Extreme-N base
stations. If you set up an Extreme N as your main and try to
connect with 802.11g Extreme or Express models, AirPort Utility
doesn’t list the necessary Wireless Mode option. If you set up an
802.11g AirPort as your main, and try to connect via Extreme N,
AirPort Utility tells you after you restart that the base station
you’re trying to connect to lacks the proper checked option.
Configure the main base station
1. In the AirPort Utility, in the toolbar, click AirPort.
2. In the Wireless view, choose Create a Wireless Network from the
Wireless Mode pop-up menu (Figure 41).
3. In the same view, check Allow This Network To Be Extended.
4. Click Update to restart the base station with that setting.
Check Allow
This Network
To Be
to make an
Extreme N
the main base
station in a
WDS network.
Page 94
Configure additional base stations
1. In AirPort Utility, in the toolbar, click AirPort.
2. In the Wireless View, select Extend a Wireless Network from the
Wireless Mode pop-up menu.
3. Check Allow Wireless Clients if you want the remote base station
to be available via Wi-Fi, not just to Ethernet-attached computers.
4. In the same view, set your Wireless Security choice and Wireless
Password to be identical with your main base station.
5. Click Update, and 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.)
Mix of Extreme N and older Extreme/Express units
1. Launch AirPort Utility, select a base station to configure, and
choose Base Station > Manual Setup (Command-L).
2. In the AirPort pane, click the Wireless button.
3. From the Wireless Mode pop-up menu, choose Participate in a
WDS Network
A WDS button appears in the AirPort pane.
4. Click the WDS button.
5. If you want this unit to act just as an Ethernet extender or a bridge
between a main and a remote, uncheck Allow Wireless Clients. In
this mode, wireless clients can’t connect to a base station, but the
Ethernet port is active and a main, remote, or relay could connect
to other base stations via WDS.
6. Set radio mode, channel, base station password, wireless security
method, and wireless password identically:
• In the AirPort pane, in Base Station view, set the Base Station
• In the AirPort pane, in the Wireless view, set the remaining
items: Radio Mode, Channel, Wireless Security, and Wireless
Page 95
7. In the WDS view, enter the AirPort ID (Apple’s name for the “air”
interface’s MAC address on a base station; see What and Where Is
a MAC Address? (p. 59) as follows:
• Main base station: Click the
button at the bottom of the
WDS Remotes list to enter the AirPort ID of the base station(s)
that you want to add, up to four total (Figure 42).
• Remote base station: Enter the AirPort ID of the main base
station in the WDS Main field.
• Relay base station: Enter the AirPort ID of the main base
station in the WDS Main field and use the
to enter WDS
remote base stations.
When configuring a main
base station,
click the
button to enter
each base
station in a WDS
network in turn.
8. I recommend testing each base station as you add it by clicking
Update (at the lower right), waiting for the base station to reboot,
and then making sure clients can connect (if enabled) and bridge
on all attached units.
If WDS has failed to work, AirPort Utility will flash the light on the
front of an Extreme N amber while displaying an amber icon next
to the base station’s icon.
Troubleshooting by double-checking or re-entering: If
you have problems after following these directions, remember that
the frequency, channel, base-station password, wireless security
method, and wireless password must all be identical on every
WDS base station (Step 6). Failing that, ensure that the MAC
addresses were entered correctly on each base station, (Step 7).
Page 96
I expect that many readers of this book already have an AirPort
Extreme from 2003 to 2006, or another 802.11g gateway. If that’s
the case for you, you may be thinking of shutting down that network
in favor of a new one. But to achieve your greatest efficiency, I’d like
to suggest that you run two networks: one operating in 2.4 GHz and
handling computers and devices with 802.11b or 802.11g built in; the
other, an Extreme N using 5 GHz and handling only newer adapters.
This is especially worthwhile if you expect to move lots of files across
your network, or use Apple TV wirelessly, where you’ll need a lot of
unimpeded bandwidth to have video stream at its best quality.
Setting up a two-band network isn’t hard, particularly because the
Extreme N has an Ethernet switch built in. The goal state for the
network is shown in Figure 43.
The finished mixed network: The Extreme G and desktop Mac are
connected to the Extreme N’s LAN Ethernet ports. A PowerBook
connects via 802.11g to the older base station; a MacBook connects
using 802.11n to the newer base station. The Extreme N’s WAN port
is connected to the broadband modem, which is in turn a conduit to
the Internet.
Page 97
Update Your Older Base Station
Your older base station needs to have three specific settings changed
in order to work in this configuration:
• Its network name should make clear that it’s a distinct network.
• Connection Sharing must be set to Off (Bridging), so that the
existing base station doesn’t create a nested set of private network
• The base station needs to obtain its address via DHCP from the
new 5 GHz base station.
NOTE If you already have a DHCP server running on a LAN, you can skip
connecting your existing base station to your new Extreme N base
station. The existing base station can obtain an Internet address
from your network’s DHCP server instead by being plugged into
any Ethernet switch on the network.
To configure and connect your old base station:
1. Launch AirPort Utility, select your existing base station, and
choose Base Station > Manual Setup (Command-L).
2. At the top of the window, click the AirPort icon, and then click the
Wireless button.
3. Change the Network Name to something descriptive, like Home
2.4 GHz or Old Slow Network.
4. Click the Internet icon.
5. From the Configure IPv4 pop-up menu, choose Using DHCP.
6. Select Off (Bridging) from the Connection Sharing pop-up menu.
7. Click Update to restart the base station with the new settings.
8. Now, plug an Ethernet cable from the WAN port of your 2.4 GHz
base station into any of the three LAN ports of the Extreme N.
Page 98
Wireless base station connections won’t work: While you
can connect two or more Apple base stations together via Wi-Fi
using Wireless Distribution System, that works only when the
base stations are using the same frequency band, channel, base
station password, and wireless security method and password.
See Bridge Wirelessly.
Configure Your New Extreme N
Next, you need to set up your Extreme N to use the 5 GHz band:
1. Launch AirPort Utility, connect to your Extreme N, and switch to
Manual Setup (Command-L).
2. Click the AirPort icon and then the Wireless button.
3. Enter a unique and descriptive name in the Network Name field,
like 5 GHz or Bust or Fast New Network.
4. From the Radio Mode pop-up menu, choose 802.11n only (5 GHz).
5. Click the Wireless Options button and check Use Wide Channels.
(This option is available only in certain countries, including the
United States.)
6. Click the Internet icon.
7. Make sure that Connection Sharing is set to Share a Public IP
Address (bottom pop-up menu).
8. Click Update to restart the base station.
Now you have two independent Wi-Fi networks operating at peak
performance without contention between them.
Put Printers in the Right Place
A number of readers of the first edition of this book wrote in after
reconfiguring their networks as described above because their printers stopped working. After some troubleshooting, we collectively
discovered that printers needed to be moved from the old 802.11g
network to the new Extreme N network to work reliably.
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A setting change was also needed. Follow these steps:
1. Unplug your USB printer from the old base station; you needn’t
power down the printer unless you also plan to move it.
2. Plug the USB printer either directly into the new Extreme N base
station, or into a USB hub that’s plugged into the base station.
3. Launch AirPort Utility, connect to your Extreme N, and switch to
Manual Setup (Command-L).
4. Click Printers on the toolbar, and confirm that the printer appears
in the list of printers shown.
5. If you are plugging the Extreme N into a larger LAN, check the
Share Printers over Ethernet WAN Port box so that computers on
that larger network can access the printer, too.
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When you share an Internet connection among one or more computers on a local network using private addresses, you give up 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.
Extreme N and AirPort Utility mark a major breakthrough for Apple,
finally adding features that have been found in other gateways for
years, but adding the usual Apple twists: their products are later than
similar ones from competitors, but they are easier to use. You can
choose from three 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, the Extreme N also lets 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 whole mapping system work
consistently with less effort. I cover these options beginning on
the next page.
• Punch through from certain programs: A protocol from
Apple just starting to become more widely used, called NAT-PMP
(NAT plus Port Mapping Protocol), helps with port mapping
without requiring any special configuration on a computer or
a base station. You can find out more in Punch Through from
Certain Programs.
• 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 if it’s directly connected to the Internet.
I describe the default host option in Set a Default Host for Full
Page 101
Map Ports for Remote Access
Port mapping relies on network address translation (NAT), which
I’ve noted only in passing previously in this book. 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 a sidebar on the next page.)
When, for instance, a LAN-connected computer wants to retrieve
a Web page, that computer might send a request from its IP address
( 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 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
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.
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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
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.
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
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You might wonder how software like iChat and Skype works
behind a NAT gateway, because it seems like they have two-way
communication where it shouldn’t be possible. Both systems hide
the fact that central servers are involved in connecting chatters:
• iChat: In iChat, the central server is run by AOL, as iChat is
part of the AOL Instant Messenger network. Each person using
iChat connects to the AIM server, which maintains a persistent
connection to iChat using the channel that iChat opened up.
The server coordinates among everyone chatting to move
messages among all those connections.
• Skype: Skype uses a different method, because it’s
decentralized. Instead of using one central server, Skype uses
what it calls supernodes, or Skype clients on publicly reachable
IP addresses that can coordinate connections among NATconnected Skype users. Your computer can be picked as a
supernode without you ever knowing it, but because the system
is so distributed, that shouldn’t affect any given user unduly.
This is also how services like GoToMyPC and LogMeIn work,
where you can remotely connect to a Windows computer when
on the road: the software on the computer maintains an open
connection to the remote-control firm’s servers.
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 44). In
the figure, I show the example of operating a Web server and playing
Half Life behind a NAT gateway.
Using port mapping reliably has two parts: set a persistent private
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
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One user on a laptop is playing Half Life 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 Half Life, the
gateway connects traffic from a player at Indiana University with
our network’s laptop user.
Set a reserved address
Before the Extreme N, you had to use a variety of complicated workarounds to maintain a private NAT-enabled address on an AirPort
network. Now, you can create this with just a few keystrokes and
For each computer with which you want to use port mapping, you
should create a DHCP reservation, which I describe fully in Reserved
addresses, earlier.
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I recommend creating a text file or other simple list that contains
a list of your computers in some descriptive way—the owner or its
unique name—and the corresponding reserved addresses.
Once you’ve reserved addresses, you can set up effective port
Dynamic addresses don’t cut it: 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 Extreme N configuration and
restarting—which changes the IP addresses assigned
Set base-station-to-computer port mapping
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.
Let’s look first at the simple example of setting up that Web server,
along with setting up ports for other services. First, we need to configure the firewall on the computer that’s acting as a Web server. The
firewall protects the computer from unwanted inbound connections,
and must be set to allow the ones you do want. Second, we need to set
up the base station to pass traffic to the newly configured port.
Running a Web server in non-server versions of Tiger:
1. Open the Sharing preference pane, and click the Firewall button.
2. Look at the upper left corner of the Firewall view. If you see
Firewall Off, click the Start button.
3. To allow inbound Web server requests, make sure Personal Web
Sharing is checked. (If you’re using Apple’s built-in Web server,
the firewall On box for Personal Web Sharing is checked
4. To allow requests for other ports or for a non-Apple Web server,
click the New button, choose Other from the Port Name menu,
and fill out the entries for ports as discussed a few pages ahead in
Configure the Extreme N for other ports.
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Running a Web server in Windows XP and Vista:
Typically, you use third-party firewall software for added security,
and these packages allow you to enter exceptions for particular ports,
such as port 80; read their instructions for details. But Windows XP
and Vista each come with a built-in firewall package that you can
configure quite simply:
1. Open Control Panel from the Windows menu.
2. Open Windows Firewall.
3. In Windows Vista, click Change Settings to the right of the
Windows Firewall text, and then click Continue when prompted.
4. In the General pane, make sure the firewall is set to On, and Don’t
Allow Exceptions should be unchecked.
5. In the Exceptions pane, click Add Port.
6. Enter Web Server in the Name field, and 80 in the Port field.
7. Click OK, and then OK again.
Configure the Extreme N to pass through to the Web server:
With the server set up to accept connections, we now can configure
the Extreme N in this fashion:
1. Launch AirPort Utility, select your Extreme N, and choose Base
Station > Manual Setup (Command-L).
2. Click the Advanced icon at the top of the window, and then click
the Port Mapping button.
3. Click the
button to bring up the Port Mapping Setup Assistant
(Figure 45).
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After you
Web Sharing
from the
Service popup menu,
the correct
ports are
4. From the Service pop-up menu, choose Personal Web Sharing
(really, this means any kind of Web server). (For a more advanced
network setup, described on the next page, enter all the necessary
ports in this step.)
5. Enter the reserved IP address in the Private IP Address field. (You
can edit only the last number of the IP address, as the first three
numbers are set in DHCP configuration.)
6. Click Continue.
7. In the next screen, enter a description for the entry so you can
recall later what you meant by it.
8. Click Done.
9. Click Update to restart your base station with this setting.
After restarting the base station, you should attempt to make a connection from outside your network to the service you enabled, or have
a friend or colleague initiate the connection. If the connection doesn’t
work, make sure the firewall on the computer running the service is
configured correctly.
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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 alternate-port servers.
You should reserve using alternate-port servers to special purposes
or 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. Using port mapping, you would set one’s public port
to be port 80, and the other to be 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 having
to make any changes on the Web server, and renders the sites
completely reachable.
Configure the Extreme N for other ports:
We won’t all run Web servers on our private networks, however,
so let’s look at the options in the Port Mapping Setup Assistant more
closely (Figure 45, previous page); these settings are nearly identical
to those used when adding new ports to Tiger’s firewall, too:
• Service: This pop-up menu is prefilled with the ports needed for
many common services, like FTP for file transfer and SMB/CIFS
(Windows File Sharing). If what you need isn’t in that list, you
have to look further.
For games and other more complex services, read the documentation for the game or program, which typically describes the portmapping settings needed. You can also consult this extensive list:
• UDP and TCP: These two different kinds of packets can be carried
over an IP network. UDP (User Datagram Protocol) is often used
for streaming media, while TCP (Transmission Control Protocol)
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handles Web and other kinds of connections. Any service you might
want to use could have a combination of UDP and TCP ports.
• Port(s): Each field for entering ports can handle a single number
or a range as two numbers separated by a hyphen. You can have
multiple numbers or ranges separated by commas. For instance
407, 1216-1300, 6000-7000 would be a legitimate entry.
• Bonjour advertising and service type: You can use Bonjour
network discovery to allow access to various services by name
via the WAN port. Typically, this means that in a program that
supports Bonjour, like Safari, any Web site that you offered up
via port mapping would appear in the browser’s list of Bonjouradvertised Web sites. (In Safari, choose Bookmarks > Bonjour,
and the program lists any Web sites available in this fashion.)
Punch Through from Certain Programs
Apple has developed a new protocol to help with port mapping
without requiring special configuration on a computer or a base
station: NAT-PMP (NAT plus Port Mapping Protocol) 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.
NOTE Stuart Cheshire, an Apple employee, created both Bonjour (also
known as zeroconf for zero configuration, in the wider Internet world)
and NAT-PMP. I knew of him back when he was a grad student,
writing about latency for TidBITS: http://db.tidbits.com/series/1014.
You can read his Internet Engineering Task Force (IETF) draft of the
NAT-PMP spec at http://files.dns-sd.org/draft-cheshire-nat-pmp.txt.
To enable this feature, select your base station in AirPort Utility,
select the Internet pane, and, in the NAT view, check Enable NAT
Port Mapping Protocol. Click Update.
The downside to the NAT-PMP protocol is that each program must
have built-in support built in to work with the protocol. With regular
port mapping, software can be entirely unaware that it’s not exposed
to the Internet.
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Apple notes that for Macs behind NAT gateways, .Mac can sync its
mountable iDisk more easily with NAT-PMP turned on, because that
lets .Mac initiate remote connections to those Macs. With iChat AV,
Apple told me that NAT-PMP enables more reliable initiation of file
transfers when the feature is enabled on base stations on both ends.
There’s not yet widespread use of NAT-PMP, because it’s not found
in routers outside Apple’s. However, as Apple continues to sell its
routers in great numbers, it’s more likely that applications will enable
the feature.
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 Extreme N 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:
1. Launch AirPort Utility, select your base station, and choose Base
Station > Manual Setup (Command-L).
2. Click the Internet icon at the top of the window, and click the NAT
3. Check the Enable Default Host At box and enter the last number in
the IP address for your default host (Figure 46).
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To set up
an exposed
check Enable
Default Host
At and enter
the private
IP address’s
last number.
4. Click Update to restart the base station with these settings.
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With a base station set up to handle local computers and hooked into
the Internet, your next step may be to attach a USB printer to the
base station so that it can be shared among all the local computers.
To attach more than one USB device to the base station, such as a
USB printer and a hard disk, or more than one of either, you need
to attach a USB hub to the base station, and then attach the devices
to the hub. I recommend a Hi-Speed powered hub that uses external
AC power; this ensures greater reliability.
Add a Printer
For each printer you want to attach to the Extreme N:
1. Plug the printer into the base station or USB hub. You should not
need to reboot your base station for it to recognize the printer.
2. Give the printer a custom name and share it over a larger LAN or
the Internet; see “Rename and Widely Share a USB Printer,”
3. As needed, configure recent Macintoshes to connect to the printer;
Add a Shared Printer in Mac OS X explains how.
4. As needed, configure Windows XP and Vista machines to connect
to the printer; Add a Shared Printer in Windows XP and Vista has
Rename and Widely Share a USB Printer
Your first task in setting up a printer is to get it working with respect
to your base station. You can assign the printer a custom name that
appears on the network during set up. Follow these steps:
1. Launch AirPort Utility and connect to your base station, and
choose Base Station > Manual Setup (Command-L).
2. At the top of the window, click the Printers icon to open the
Printers pane (Figure 47).
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You can
change a
name as it
appears on
the network.
3. Enter a name for the printer in place of the default name, or leave
the name that AirPort Utility prefilled in place. This name will
appear in the Print dialog when you select a printer or print.
4. Check Share Printers over Ethernet WAN Port to make the printer
available to other computers on a larger LAN (and even over the
Internet if the Extreme N has a public IP address).
5. Check Advertise Printers Globally Using Bonjour to make the
printer browsable over a larger LAN (outside the base station’s
private network) from all Mac OS X machines, and from Windows
machines with Bonjour installed.
6. Click Update to save this change and restart the base station.
NOTE Apple briefly offered a list of supported USB printers when this
shared capability first appeared, but they withdrew this list years
ago when it became, in their words, “unwieldy” to maintain. If the
steps above don’t work, your printer may be unsupported—for more
info, read the last suggestion in Troubleshoot an Unavailable Shared
USB Printer (ahead about six pages).
You should also consult iFelix’s unofficial list of USB printers
that work with an AirPort Extreme or Express base station at
http://www.ifelix.co.uk/tech/1013.html for the Extreme 2003
and at http://www.ifelix.co.uk/tech/8013.html for the Extreme N.
It contains the original Apple list supplemented with details from
readers of the page and tested by iFelix’s maintainer.
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Add a Shared Printer in Mac OS X
Follow these steps to set up printing from a Macintosh running
Jaguar (you need at least Mac OS X 10.2.7), Mac OS X 10.3 Panther,
or Mac OS X 10.4 Tiger to a shared USB printer:
1. Open your printer utility from the /Applications/Utilities
folder. In Jaguar, it’s called Print Center. In Panther and Tiger, it’s
called Printer Setup Utility.
2. Click the Add icon.
3. Now:
• In Jaguar and Panther, choose Rendezvous from the top pop-up
menu. Then, find your printer in the resulting list, select it, and
click Add.
• In Tiger, click the Default Browser icon at the top, if it’s not
selected already.
Your printer should appear in the list. However, if your printer
doesn’t show up, try the suggestions offered ahead in Troubleshoot an
Unavailable Shared USB Printer.
Now, your printer connection is set up. You can print from any
application offering a Print command—just choose the printer from
the Printer pop-up menu in the Print dialog.
NOTE You can also add a printer from the Print dialog. From the Printer
pop-up menu choose the printer from the Shared Printers submenu,
if it’s there. If not, then choose Edit Printers or Add Printer (which
command you see depends on the version of your operating system).
After you add the printer, it shows up in the list of printers in the
Print pop-up menu.
Warning! Don’t choose the printer from the Shared Printers
submenu again, or you may create yet another instance of the
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Add a Shared Printer in Windows XP and Vista
We can do it the hard way or the easy way. Let’s try easy first: Bonjour
for Windows! (I recommend Bonjour because it is easy to set up, but
if you prefer to not install additional software, I also give directions
for setting up a printer without Bonjour in Windows XP and Vista,
Apple lets you add Bonjour network resource discovery in Windows
XP and Vista with the free, downloadable Bonjour for Windows
package from Apple at http://www.apple.com/support/downloads/
Once you’ve installed the package, make sure your printer is turned
on and follow these steps to add printers shared by the base station:
1. Launch the Bonjour Printer Wizard and click Next.
2. Select a printer and click Next.
3. Choose a printer driver if one hasn’t been selected automatically
for you, and click Next.
4. Click Finish to install the printer.
The printer is now available to all applications.
Add a shared printer in Windows XP
The following advice comes in general form from Mac OS X Hints
(http://www.macosxhints.com/), a great Web site for technical
advice. I was initially stymied in my attempt to convince my Windows
XP box to print to a shared USB printer, and the advice on Mac OS X
Hints was of great help in getting started. Here are the steps, which
you should follow after making sure your printer is on:
1. From the Control Panel, open Printers and Faxes.
2. From Printer Tasks in the list of tasks in the left navigation bar,
click Add a Printer.
3. The Add Printer Wizard appears. Click Next.
4. Select Local Printer Attached to This Computer. Uncheck Automatically Detect and Install My Plug and Play Printer. Click Next.
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5. Select Create a New Port (near the bottom of the screen). Choose
Standard TCP/IP Port from the pop-up menu, and click Next
to launch the Add Standard TCP/IP Printer Port Wizard.
6. Click Next again to show the Add Port screen.
7. For Printer Name or IP Address you have two choices, depending
on whether the Windows machine is connected via Wi-Fi or
Ethernet to the base station LAN, or is outside that LAN (either
on a larger LAN or remotely printing over the Internet):
• Within the base station LAN: Enter your base station’s
LAN network address—this is the first three numbers in your
DHCP address range with a 1 in the fourth number’s position,
• Outside the base station LAN: Enter the base station’s
WAN IP address.
Leave Port Name alone; Windows will fill it in for you. Click Next.
8. On the next screen, choose Hewlett Packard Jet Direct from the
pop-up menu next to the Standard radio button. I don’t know why,
but Mac OS X Hints found that it works. We obey. Click Next.
9. Click Finish to return to the first wizard. From the list of manufacturers and printers, select your precise model. Click Next.
10. The final screen has you name your printer. By default, it uses
the name from the model type in the previous screen. You can
enter a new name if you’d like, however. Select whether or not
you want this printer to be your default by clicking the Yes or
the No radio button. Click Next.
11. Leave the Do Not Share This Printer radio button selected unless
you want this computer to share the printer to other computers,
which makes no sense given that it’s already a shared printer,
right? (If you must be contrary, click the Share Name radio button
and enter a name.) Click Next.
12. Choose to print a test page by leaving the Yes radio button
selected, which is the default, and click Next.
13. Finally, click Finish.
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14. Walk over to your printer, and see if a test page was printed.
If the page printed, you’re ready to go. If not, check through the
preceding steps to make sure you configured everything correctly
or try the suggestions in Troubleshoot an Unavailable Shared USB
Printer, two pages ahead.
Add a shared printer in Windows Vista
Vista streamlines the process of adding a shared USB printer to a
Windows setup, though not as much as Bonjour (covered a few pages
earlier). Here are the steps, after making sure your printer is on:
1. From the Windows menu (the icon in the lower left of the screen),
click Control Panels.
2. Double-click Printers.
3. From the menu bar at the top, click Add a Printer.
4. Click Add a Network, Wireless, or Bluetooth Printer.
5. After a moment, the printer should appear in the list of available
printers. Select it and click Next.
(If the printer doesn’t appear, skip ahead to “Additional Steps,”
next page.)
6. Vista now contacts the printer to obtain the printer’s information,
such as its name. If all is well, Vista will suggest you use a currently
installed driver for the printer. Click Next.
7. If you want the printer to appear in Vista with a different name,
enter that name. Click Next.
8. Click Print a Test Page. Then click Close in the test page window
and Finish in the Add Printer wizard.
If the page printed, you’re all set. If not, go through the preceding
steps again to make sure you configured everything correctly or try
the suggestions in Troubleshoot an Unavailable Shared USB Printer,
two pages ahead.
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Additional Steps
If your printer didn’t show up in Step 5, continue with these steps:
1. Click The Printer That I Want Isn’t Listed.
2. Select Add a Printer Using a TCP/IP Address or Hostname, and
click Next.
3. In the “Hostname or IP Address” field, enter an address based on
your Vista computer’s position in the network: connected via Wi-Fi
or Ethernet to the base station LAN, or outside that LAN (either on
a larger LAN or remotely printing over the Internet):
• Within the base station LAN: Enter your base station’s LAN
network address—this is the first three numbers in your DHCP
address range with a 1 in the fourth number’s position, like
• Outside the base station LAN: Enter the base station’s
WAN IP address.
Leave Port Name alone, as Vista prefills it as you type. Click Next.
Vista tries to find the appropriate printer driver. In my testing, it
fails at this stage, and requires manual selection. If Vista succeeds
in finding the right driver, resume at Step 7 on the previous page.
4. Otherwise, in the screen that results—Additional Port Information
Required—choose Hewlett Packard Jet Direct from the Standard
pop-up menu. (Don’t ask why; just do it!) Click Next.
5. Now:
• If your printer maker and model show up in the list, first select
the maker on the left and second the model on the right; then
click Next. Leave Use the Driver That Is Currently Installed
unchecked, and click Next.
• If you don’t see your printer maker and model listed, insert a
disk that came with the printer and click Have Disk to install a
driver that way. Click Next and follow the resulting directions.
6. Resume at Step 7 on the previous page!
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Troubleshoot an Unavailable Shared USB Printer
If you followed the directions earlier in this section and you can’t
print to your shared USB printer, one of the following suggestions
should shed light on the problem:
• Make certain that the printer is powered up and not in an error
condition (such as out of paper or out of ink).
• Make sure your computer is on the same network as the base
station (on the computer, launch AirPort Utility and make sure
the base station appears in AirPort Utility’s left-hand list of base
• Make certain the base station recognizes the printer: use the
instructions in Rename and Widely Share a USB Printer.
• Using AirPort Utility, restart the base station and try again.
• Consult the suggestions from Apple at http://docs.info.apple.com/
article.html?artnum=107418. Note that the last suggestion, under
“Still not working?” is to confirm that your printer is able to work
with AirPort printer sharing. Apple has linked to Lexmark and
HP’s list of compatible printers.
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Extreme N adds an interesting option for sharing disks across a
network without attaching them to a computer. The base station can
share attached drives over a network both via the standard Apple
Filing Protocol (AFP) format, the same format used with Personal
File Sharing and Mac OS X Server share files, and via Samba, a
network file-sharing service compatible with Mac OS X, Windows,
and Linux.
Warning! There’s no way to share volumes via either only AFP
or only Samba; you have to share through both.
You can connect a single drive to the USB port on the Extreme N, 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.
You must format mountable disks before you attach 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.)
Warning! Before you format anything, read Grant Access,
ahead, to learn the quirks that can arise with different formats
and different types of access.
Warning! Unix, Microsoft NTFS, and other partition formats
are not supported.
Once one or more drives are connected, you can access them and let
others access them, too. You handle all the configuration in AirPort
Utility in the Disks pane.
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Slow Speeds Ahead! The performance of base-stationconnected drives is slow to creeping, when compared to network
throughput and to the speed of reading and writing to a drive
connected to a computer.
In my tests of the Extreme N (gigabit), I saw speeds about onethird that of directly connected USB drives when transferring
larger files. When I copied 8,000 tiny HTML files—documentation
for a program, the transfer speed dropped to below 10 percent
of directly connected USB. This is partly due to inefficiencies
in copying many small files in AppleShare File Protocol (AFP),
and partly due to the low-power, but adequate, processor in the
Extreme N (both models). For networks in which speed is an issue,
use a computer-based fileserver or dedicated network-attached
storage (NAS) device.
Here’s a guide to file-sharing concepts that 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+, FAT16/32, or NTFS—
determines how data is written to the disk; each operating system
supports a different set of formats.
• 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, Extreme N makes
folders into volumes, so that you can control access more finely, as
described ahead.
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Viewing Connected Volumes
In AirPort Utility, the Disks view in the Disks pane offers a little
information and one option. Each disk connected to the base station
is noted in a list on the left, and each partition on that disk is found
by clicking the triangle next to the disk name (Figure 48). Selecting
a partition reveals the capacity of that partition, the used and remaining storage, and how many users have mounted the partition.
In this example, AirPort Utility shows two partitions for the drive
attached to the base station. Selecting the partition shows storage
information and connected users.
Clicking Disconnect All Users shuts down all file service, forcing
connected users’ computers to lose a connection with mounted
volumes no matter whether they have open files or transfers in
progress, so click it with care. It’s better to have each user (or you)
unmount each connected volume first. If you do disconnect users
by clicking the button, Mac OS X warns you in AirPort Utility and
informs each user with an alert message (Figure 49). This button
appears even if no users are connected.
When no users are connected, the drive is in a standby state that lets
you unplug it from the Extreme N without harm.
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Disconnect All
Users brings
up the warning
(top) about the
to users still
working on data
stored on those
If you want to
bump working
users off,
AirPort Utility
obliges and Mac
OS X complains
Grant Access
Apple offers relatively little granularity in setting up security and
access for hard disks you connect to an Extreme N. You can choose
only one of three methods for setting passwords, and you can’t set
permissions individually for folders or files on each hard disk, nor set
permissions differently for different partitions or different hard disks.
Kinds of access
AirPort Utility has three ways to grant access, found in the Disks
pane, in the File Sharing view, in the Secure Shared Disks pop-up
menu (Figure 50).
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Utility offers
three options
for securing
a shared
disk by
the level of
The three ways to grant access are:
• With Base Station Password (default): This self-explanatory
option is the default method, and means that only a single password is used to secure the base station’s settings and any attached
hard disks. This option is good for home and small networks in
which you’re not concerned about someone changing the settings
on a base station.
• With a Disk Password: This sets a password that controls
access to all disks; this password is distinct from the base-station
password. All users accessing the disk have access to all files. This
works for a small network where you want to make sure those with
fileserver access can’t modify the base station, even unintentionally.
• With Accounts: On partitions formatted with HFS+, you can
set up individual user names and passwords, each with different
levels of access; these accounts are distinct from any Mac OS X or
Windows user accounts set up on the computer that’s configuring
the base station. An Accounts button appears, and you can click
it to add and edit users. User access options can be set to Read
and Write, Read Only, and Not Allowed. (That last option lets you
disable an account without removing it.)
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Accounts are useful for larger networks, but they are a new feature
and still have some quirks that I hope Apple will work out soon:
No directory services: You can’t yet tie in network directory
services with this option, so accounts must be entered one at a
time and manually updated.
Inconsistent partition-to-account matching: With
partitions formatted using HFS and named accounts, you can’t
choose which HFS+ partition winds up containing the userspecific account folder. In my testing, it seemed arbitrary, and
even moved from partition to partition after changing seemingly
unrelated settings and restarting the base station. All other
partitions formatted with HFS+ are served as single, wholepartition volumes, which is a related bug or missing option.
This could result in the strange circumstance in which you
attach a 1 terabyte (TB) disk drive and a 1 GB flash drive to
your Extreme N, and the unit puts user accounts on the smaller
drive. I expect Apple will add an option to select the volume
on which user accounts are created to solve this.
Single drive, no worries: With a single hard disk that’s
formatted in HFS+, you won’t see this problem.
Paired with each of the three ways to grant access is the Guest Access
pop-up menu. You can set those without a password to have full
access, read only, or no access.
Other network settings for file sharing
You can limit access to what network or part of a network is available
through two related checkboxes beneath Guest Access:
• If you check Share Disks over Ethernet WAN Port, other
computers on a larger network or the Internet can access your
base-station fileserver.
With the Share Disks box checked, you can also check Advertise
Disk Globally Using Bonjour. This option has risks, too, as it ties in
your fileserver access with a globally registered domain name that
could expose you more broadly than you intend.
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Warning! If you enable WAN access and the Extreme N has a
public IP address, you are exposing your files to a larger potential
audience of crackers and ne’er-do-wells, so it becomes critical to
set guest access appropriately. Or, you can use a firewall between
the Extreme N and the larger world to provide additional access
control, such as limited fileserver access to particular IP ranges
that represent other locations you work for or remote offices.
• The other option in this section lets you configure Windows
File Sharing—more frequently called Samba—by naming the
Workgroup and choosing a WINS Server. The Workgroup name
allows other Samba-capable computers to organize fileservers into
a group for display. The WINS server, if there’s one on your network, provides a separate name-based association for Windows
computers to the IP address on your base station.
Gain Access
You or users on your network can access disks connected to an
Extreme N in two ways:
• With the new AirPort Disk Utility, which can identify drives as they
appear using Bonjour
• With normal file-sharing connection options, such as Connect to
Server in the Mac OS X Finder
Before we look at methods of accessing shared disks, though, we need
to figure out precisely which volumes are mounted based on the
settings on a given base station, the disk’s format, and what kind of
access you’re attempting to gain. I lay out the options in Table 4,
because they’re too baroque to explain conversationally.
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Table 4: Comparing Methods of Serving Shared Disks
Base station
or disk
Password The entire volume is served. Users mount it as a volume
having the partition name.
A folder named Shared** is served as a volume. Users mount
it as a volume having the partition name.
HFS+-formatted partition:
How Partitions Are Served
• 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
• Any other partitions are served as volumes named with
the partition name.
FAT 16/32-formatted partition:
• A folder named Shared is served. Users mount it as a
volume having the partition name.
A folder named Shared** is created on each partition, and
users mount it as a volume named with the partition name.
* If Guest Access is set either to Read and Write, or to Read Only.
** The shared folder appears on the disk, viewable as a folder only by users with a password,
only after the first guest accesses the volume.
AirPort Disk Utility
The AirPort Disk Utility program makes it convenient to identify
base stations that are sharing hard disks. That sounds great at first,
but the utility has few advantages over other ways of accessing shared
volumes. (Versions are available for both Mac and Windows; I cover
the interface for Mac OS X here.)
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When you install the utility (see Install new software, earlier), you
can turn on a status menu that lists each base-station fileserver
(Figure 51). You can also remove this menu, and turn off automatic
notification when new shared volumes are added to any base station
on the network (Figure 52).
The AirPort Disk menu shows all base
station fileservers.
AirPort Disk Utility lets you set notification and menu preferences,
as well as allowing you to change the way you connect to base
station fileservers.
If you don’t change the utility’s default, when a new volume is added,
you’re prompted to act on it; the same is true if you choose the basestation fileserver name from the AirPort Disk menu. A dialog appears
(Figure 53) that wants to know your action:
• Ignore: Don’t notice if this volume appears in the future.
• Connect as Guest: No password required, but you can view only
shared files. (This option doesn’t display if Guest Access is set to
Not Allowed in AirPort Utility.)
• Connect with Password: This option shows up with a Username
field if, on the base station, Secure Shared Disks is set to With
Accounts; or as just a Password field otherwise.
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AirPort Disk
Utility displays
these options
for mounting
all volumes
to a base
There’s no way to tell AirPort Disk Utility to mount a single volume,
which makes the tool less than ideal if you need only a single volume.
If you want to mount all volumes at once or have only a single partition, then the utility is fine. Otherwise, I recommend using normal
volume mounting, described next.
Normal volume mounting
Fortunately for us, the file sharing in the Extreme N uses standard
methods: AFP, commonly known as AppleShare, and Samba,
Windows’s default method.
Stick to their own kind: The Extreme N fileserver shares only
HFS+ volumes as AFP volumes, while Samba can share either
HFS+ or FAT32 (MS-DOS) formatted partitions as SMB/CIFS
Mount in Mac OS X
You can mount volumes in Mac OS X by following these steps:
1. In a Finder window, click Network in the sidebar, or choose Go >
Network (Command-Shift-K).
A list of connected servers appears in the Finder window, and the
fileserver should appear in the list twice: first as an AppleShare
fileserver and second as a Samba fileserver.
2. Double-click the base station’s fileserver name to open an
authentication dialog.
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3. In the Name field:
• If you don’t have a user account because the base station is
using base-station or disk passwords enter any short bit of text
or leave the field blank.
• If you have a user account name, enter it.
4. In the Password field, enter the base station, disk, or account
5. Select the volume or volumes you want to mount and click OK.
If you are mounting a volume remotely or it doesn’t appear in Step 1,
choose Go > Connect to Server and enter the IP address of the base
station or an associated domain name (for FAT16/32 volumes, enter
smb:// followed by the IP address.) Then, follow Steps 3 to 5 above.
Mount in Windows
With Windows XP and Vista, open the network browser by doubleclicking Network on the Desktop. The base station name should
appear in the Network browser. When you connect, enter the name
and password as in Steps 3 to 5 above.
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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.
But before I delve into the details of protecting yourself from snoopers, let’s look at whether you even need to turn on security.
Likelihood, Liability, and Lost Opportunity
When Adam Engst and I were writing The Wireless Networking
Starter Kit, Second Edition, back in 2003, we disagreed over how
concerned the average home Wi-Fi networker should be about
security. Adam came up with a great formulation that I agreed with
and want to walk you through. He calls it the three L’s of security:
likelihood, liability, and lost opportunity. This framework lets you
evaluate how much security—if any—you need for your network.
NOTE If you’d like to know more about the topics in this section, read
Take Control of Your Wi-Fi Security, a companion book we wrote.
The first aspect of security to consider is likelihood: how likely is it
that someone will violate your privacy, steal your data, or otherwise
exploit you? If you live in a lightly populated area, and no one could
easily come within range of your network without sitting in your
driveway, you probably don’t have much to worry about.
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But if you live in an apartment building with neighbors who could
pick up your connection, the likelihood of someone connecting to
your network rises significantly, raising the question of whether you
want to allow others to share your Internet connection or not.
TIP Because Wi-Fi and public hotspots (free and fee) go together like
coffee and cream, it’s very likely that you’ll use a laptop on a network outside your home, too. There are a whole different set of
concerns about the likelihood of someone snarfing your data and
passwords on hotspot networks as opposed to networks you set up
yourself. We address those concerns and how to solve them in Take
Control of Your Wi-Fi Security.
The likelihood of attack increases significantly if you’re running a
business, since it’s plausible that your network would carry desirable
information such as credit card numbers, business plans, and so on.
Also, most businesses are located in areas or buildings where someone could easily sit and hack into a network without being noticed.
What is the realistic liability if someone were to record all the traffic
that passed across your wireless network? For most home networks,
the amount of network data that’s at all sensitive is extremely low;
perhaps a credit card number being sent to an ecommerce Web site
that unusually doesn’t use SSL/TLS (Secure Sockets Layer/Transport
Layer Security, a security standard for Web servers), maybe financial
data, possibly some bits that would be embarrassing if made public.
Simply allowing someone else to use your Internet connection
has a relatively low liability in most cases. However, you may think
differently if you pay per byte, if you have a slow dial-up connection
that would be impacted by someone else’s use (with high speed DSL
and cable modem connections, you’re unlikely to notice another
user), or if you’re concerned that allowing someone else to use your
connection would be violating your ISP’s terms of service in a way
that was likely to result in you being disconnected. A few scary stories
have surfaced of police obtaining a warrant, knocking down a door,
and finding an innocent person or family who had an open access
point. (For one such example, see http://www.washingtonpost.com/
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Businesses are, once again, a different story. The likelihood of sensitive and confidential information passing through a business’s wireless network is much higher, of course, and the liability of an outsider
learning that information is significantly greater. For instance, rules
protecting patient information could lead to significant fines if
a medical office or hospital had its network compromised. And if
a competitor learned confidential business plans, the ramifications
could be catastrophic.
Lost opportunity
With home wireless networks, the opportunity cost for layering on
security comes mostly in the form of troubleshooting irritating problems, which is more necessary and harder when security is on, and
in the annoyance of dealing with passwords with new machines or
when you have visitors.
Companies, even small ones, may have fewer lost opportunities
because they might have a dedicated staffer or whole department
that deals with installing, maintaining, and supporting software to
promote overall security.
Your spot in the security spectrum
It’s up to you to determine the likelihood of someone breaking in
to your network and either using your Internet connection or eavesdropping on the data that flies by. Next, you must determine the
severity of the problems that could ensue from someone using your
bandwidth or using a network sniffer to record your data. Lastly,
you need to figure out what the lost opportunity of different levels
of security is: the higher the likelihood of attack and the higher the
liability if your network were to be invaded, the more you’re probably
willing to spend and the more annoyance you’re willing to endure.
Once you’ve worked through those three thought exercises, you can
determine just how much money and effort you should expend to
secure your wireless network. Now let’s look at how you might apply
such security precautions.
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, such as employing a closed network or using MAC address
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Closed network
In a closed network, your 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
An open network appears by name in the AirPort menu or in other
places in the Mac OS and Windows 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:
1. Launch AirPort Utility, connect to your base station, and choose
Base Station > Manual Setup (Command-L).
2. At the top of the window, click the AirPort icon. Then, click the
Wireless button.
3. Click the Wireless Options button.
4. Check Create a Closed Network.
5. Click Done, and then click Update to restart the base station.
MAC address filtering
MAC address filtering initially sounds more promising than a closed
network. With this method, you enter the MAC address of every
computer you want to allow to connect to your Wi-Fi network. If a
computer’s address isn’t in the list, then that computer can’t connect.
The flaw with MAC address filtering is that any cracker worth her
salt can easily monitor a network to see which MAC addresses are
able to access the network. She can then use simple software to
modify or clone the MAC address on her own network adapter,
thus gaining access.
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TIP If you use MAC address filtering and your network has multiple base
stations, each one must have the same list of allowed MAC addresses.
You can use AirPort Utility to save one base station’s configuration,
and then import just the MAC address controls, to your other base
stations. See Export and import configuration profiles.
If you don’t want to build a security fortress against crackers, but
you do want to mediate the access for kids in your house or you want
to clarify to outsiders that you’ve restricted access, MAC address
restriction works quite well. You can also combine encryption and
MAC address filtering for a pretty good overall solution.
The Extreme N adds another element to the mix: controlling access
by time of day and day of week for particular MAC addresses.
To restrict access, first note the MAC addresses for devices you want
to limit; see What and Where is a MAC Address? (p. 59). You can also
use AirPort Utility to extract the MAC address of a computer you’re
using to configure setup.
Warning! Don’t store the base station’s password in the
Keychain on a computer that you’re restricting via AirPort Utility.
Otherwise, later, someone on that computer could quite easily
reconfigure the base station to remove those restrictions!
NOTE If you use Wi-Fi Protected Setup (WPS) to allow computers to join
the network, but limit their access to 24 hours, an entry appears in
the access control client list with a special tag. See Use WPS for
more details.
To restrict access by MAC address on an Extreme N, follow these
1. Launch AirPort Utility, select your base station, and choose Base
Station > Manual Setup (Command-L).
2. Click the AirPort icon; then click Access Control and select Timed
3. Click the
button at the bottom of the access control client list.
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4. In the Timed Access Control Setup Assistant, repeat these steps for
each Wi-Fi device you want to restrict:
a. Enter the MAC address of the computer you want to add, or
click This Computer to fill the field with the MAC address of
the computer on which you are running AirPort Utility
b. Enter a description of the computer you are adding.
c. If you want to control access time, choose restrictions: Click
button to add an entry, or select an entry and click the
to delete it.
You can choose a day of the week, weekdays (Monday through
Friday), weekends (Saturday and Sunday), or Everyday. The
time of access is either All Day or a range in the current day.
You can’t set a range of time that spans two days; that requires
two separate entries. (The combination of Everday and All
Day would be an ineffective barrier to access!)
d. Click Done.
5. You should also edit the “(default)” entry in the access control
client list. It’s set at the factory to Unlimited. If you want to exclude
all computers that aren’t listed here from having any access, select
it, click Edit, and then choose No Access from the Day pop-up
menu. Click Done.
6. Click Update after you have added all the computers that you want
to restrict.
Now, only those computers on your network whose MAC addresses
you’ve entered may connect to the network. If one can’t connect,
check that you’ve set the access time restrictions correctly.
Use Built-In Encryption
Although MAC address filtering and a closed network will deter
casual passers-by, they don’t constitute a defense. If you want a better
defense, you need to step up to encryption and password protection.
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
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Unsecured out to the Internet: The connection from the base
station to the rest of the network or the Internet has to 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 is used by the
system 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. See Table 5 for side-by-side comparisons. I look at
each option in more detail next.
Table 5: Wi-Fi Security Compared
What Can Use It?
Any Wi-Fi adapter using 802.11a,
b, or g, including the earliest
Encryption easily broken;
deprecated since 2003
WPA Personal
Works with original AirPort Card
(10.3 or later), and with many
early adapters with new firmware
Requires slightly newer computers
and operating systems; no Mac
OS 9 or earlier support
Works only with gear shipped
starting in late 2002, including
AirPort Extreme, but requires
10.3 or later, or Windows XP SP2
or Vista
Older machines can’t connect,
including those with original
AirPort Card
Allows mix of WEP and
WPA/WPA2 Personal
Doesn’t seem to work consistently;
doesn’t allow robust security
Supported in Mac OS X 10.2 or
later, Windows XP SP2, and Vista
Requires back-end server to
handle account management
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WEP (Wired Equivalent Privacy) allows the use of a 40-bit or 104-bit
password, the equivalent of 10 or 26 hexadecimal digits, or 5 or 13
text characters, respectively. WEP was never designed to be very
strong, and cracks, or ways to retrieve the encryption key by watching
network data, started to appear in 2001. It’s acceptable for home use,
but I wouldn’t rely on it as a business.
You could use WEP to signal that your network is off limits. In some
U.S. states and in some countries that “no trespassing” intent could
result in an interloper between charged with a computer crime and
even convicted, as recent cases in Florida, Alaska, and Singapore
WPA & WPA2 background
WPA (Wi-Fi Protected Access) was introduced by the Wi-Fi Alliance
as an interim measure when work by an IEEE committee—802.11i—
was taking too long. Released in 2003, 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
Mac OS X 10.3 or later; see http://docs.info.apple.com/article.html?
artnum=107795 for Apple’s requirements and software links. (The
original 802.11b AirPort Base Station cannot be upgraded.)
WPA2 was the final version of WPA security that includes all the
work done in the 802.11i committee. WPA2 can use the weaker,
but still relatively secure form of encryption offered in WPA. But
WPA2 significantly adds a government-grade method favored by
corporations. Any equipment released in 2003 or later can handle
WPA2. The Extreme 2003 and 2007 and AirPort Express all handle
WPA2, but Mac OS X 10.3 or later is required to use it. The original
AirPort Card cannot access WPA2-protected networks.
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The difference between WPA and WPA2 is that the former offers
an encryption method that’s a repaired version of WEP, known as
TKIP (Temporal Key Integrity Protocol). WPA2 adds AES-CCMP
(Advanced Encryption System, Counter-mode CBC-MAC Protocol,
whew), which incorporates the U.S. government-backed AES
method limited to 128 bits. WPA2-enabled Wi-Fi adapters may
use either TKIP or AES-CCMP to connect.
The Extreme N can offer WPA/WPA2 protection, in which both older
and newer devices can join with either form of key; or it can offer a
WPA2-only network, in which only computers that support WPA2’s
advanced encryption key type can join.
NOTE On 802.11n networks that are set to use only 802.11n, WPA2 is the
minimum level of security. This makes sense because all 802.11n
devices must support WPA2.
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.
This makes a WPA/WPA2 passphrase memorable, and the length
adds entropy, the principle of adding greater disorder to make it
harder to use brute force to uncover a key. A key could look like my
d000gs have lite_brite_hair! I kid you not.
TIP Researchers believe 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.
Choosing short passphrases that combine a random assortment
of numbers, letters, and punctuation; or longer passphrases with
a few punctuation marks defeats this problem, as in the example
passphrase above.
The Enterprise flavor of WPA and WPA2 requires a server to manage
accounts, but simplifies access by letting people enter a user name
and password—one that might be shared for resources across a
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network, including fileservers—and receive a unique encryption key
that they never need to know about.
TIP Even small offices might like to use WPA/WPA2 Enterprise, and
a few companies offer affordable ways to add it to an Extreme N:
• You can buy server software from Periodik Labs
(http://www.periodiklabs.com/shop/, $750).
• You can use a hosted option in which the server is located outside
your network and you use a Web site to add and delete users.
I recommend WiTopia’s SecureMyWiFi (http://witopia.net/
securemore.html; $20 setup and $10 per month for up to five
users, $100 setup and $100 per year for up to 100 users).
Turning on WPA/WPA2 with AirPort Extreme
Here’s how to enable WPA/WPA2 or WPA2 only:
1. Run AirPort Utility and select your base station. Choose Base
Station > Manual Setup (Command-L).
2. Click the AirPort icon. Then, click the Wireless button.
3. From the Wireless Security pop-up menu, choose WPA/WPA2
Personal or WPA2 Personal.
Warning! Macs with the original AirPort Card can’t connect to
WPA2 Personal-configured networks.
4. Enter a key of 8 to 63 characters in the Wireless Password field
and the same key again in the Verify Password field.
5. Click Update and 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 Computers, earlier.
WEP Transitional
The Extreme N supports WEP Transitional, a rare and interesting
security mode that I and colleagues have found to be problematic and
buggy in actual usage. WEP Transitional lets you mix older WEP-only
Wi-Fi connections with newer WPA/WPA2 connections.
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The problematic part is conceptual: the network encryption is as
weak as the weakest link. Using WEP Transitional leaves you vulnerable to the same cracks that affect plain WEP. The buggy part is that
it’s seemingly erratic whether computers can connect via WEP, WPA,
or WPA2 in this mode. Apple will surely fix that—we hope.
If it’s necessary for you to mix modes, or occasionally allow WEP
clients on your network, here’s how to set this up, but I warn you
that it might not work at all:
1. Run AirPort Utility and select your base station. Choose Base
Station > Manual Setup (Command-L).
2. Click the AirPort icon. Then, click Wireless.
3. From the Wireless Security pop-up menu, choose WEP
(Transitional Security Network).
4. Your WEP password must be exactly 13 characters, although Apple
doesn’t note this until you try to update the configuration. Enter
the WEP key in the Wireless Password and Verify Password fields.
5. Choose Base Station > Equivalent Network Password.
A dialog appears, showing the WEP key you just entered, which
is also the key you use as a WPA passphrase to join the network
(Figure 54). The dialog shows the 26-digit hexadecimal WEP key
for older devices or those that can’t handle ASCII WEP keys.
You can select and then copy—Edit > Copy—either key from the
dialog. (This isn’t an error in this book: You can really select and
copy within this dialog.) Also, if you ever forget or misplace the
keys, you can also later follow these steps again to retrieve the key.
The Equivalent
Password dialog
shows you the
needed to gain
access using
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6. Click OK, and then click Update and wait for the base station to
The next time you or another user tries to connect to the network,
whatever operating system you’re using will prompt you for a password to gain access. You can find details on connecting to a network
in Connect Your Computers, earlier.
WPS, Wi-Fi Protected Setup, lets a computer or other Wi-Fi device
join a WPA/WPA2 Personal protected network without entering a
key. Instead, in the two versions that Apple has implemented, you can
join without a password or via a simpler PIN (personal identification
number). Apple’s use of WPS requires that you connect to the base
station using AirPort Utility and, while connected, have the device
that wants to join the network attempt to join.
Warning! The only Macs that support WPS at the moment are
those that have 802.11n adapters in them with the latest software
installed. Windows XP SP2 and Vista don’t seem to yet have builtin support. As an industry-wide standard, WPS will appear in
more operating systems and more base stations during 2008.
For either kind of WPS, follow these steps to get set up:
1. Connect to your base station via AirPort Utility and choose Base
Station > Manual Setup.
2. Choose Base Station > Add Wireless Clients to open the Wireless
Client Setup Assistant (Figure 55).
The assistant allows
a client to join the
network without a
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3. If you like, you can check Limit Client’s Access to 24 Hours, perhaps for a visitor. This will put a special restriction on the account
in its access control settings after you finish the configuration
(Figure 56). (See MAC address filtering for more detail.)
The special 24-hour
limit entry for timed
access can’t be
edited for time, only
by name and MAC
4. Select PIN or First Attempt, and then click Done.
This puts AirPort Utility and the base station into a state of
watchful awareness! AirPort Utility notes that it’s waiting for
a connection.
5. On the client machine, look in the AirPort status menu on the
menu bar for the network name, which appears in bold. Choose
that network name (Figure 57).
The network with WPS standing by
appears in bold: Draft N Network.
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6. Now:
• If you’ve selected the First Attempt option, the first computer
that tries to connect to the network after this point is presented
with an encryption key automatically.
• If you’ve selected a PIN, the Mac OS X system that’s trying
to connect generates a code onscreen that you must enter in
AirPort Utility. A key is then exchanged between that computer
and the base station, and that computer joins the network.
7. AirPort Utility’s watchful-waiting dialog disappears, and AirPort
Utility confirms that the device has been added. This lone operation, out of all others on the base station, requires no Update to
The client is now connected.
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Interference from other Wi-Fi and non-Wi-Fi devices using the
same spectrum is one of the most frustrating problems to deal with
in making your AirPort network work well. Let’s first look at eliminating sources of conflict, and then at a mysterious option Apple offers
that seems to help as well.
Eliminate Conflicting Signals
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, these ideas 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 GHz:
• Run iStumbler (http://www.istumbler.com/) to determine whether
other networks are running in the vicinity. iStumbler 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.
• Investigate your cordless phones and microwave oven as culprits—
they can both create static on the Wi-Fi line; see Set Interference
Robustness (ahead). Do you have problems only when talking on
the phone or making popcorn? There you go.
• Also check if you have problems while Bluetooth devices are in use.
Older Bluetooth equipment can interfere with Wi-Fi networks.
• Do you live in an area 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 switch to 5 GHz to overcome that problem.
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• If you’re desperate for a solution, check out Wi-Spy, a relatively
inexpensive spectrum analyzer. It can show whether there’s interference beyond Wi-Fi. (See Testing from client to base station.)
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 using an unused band (swapping
2.4 GHz for 5.8 GHz or vice versa). Or swap your Wi-Fi from
2.4 GHz to 5 GHz, a potentially expensive proposition, but one
guaranteed to produce better results.
• In 5 GHz, use lower-numbered channels; 5.8 GHz is in the highest
range of channels supported by the Extreme N. (This also works
for wISP interference.)
• Try T-Mobile’s HotSpot@Home, which offers cordless calling from
a cell phone that also includes a Wi-Fi radio. You make and receive
unlimited U.S. calls for $20 per month (one line) or $30 per
month (2–5 lines) over your own Wi-Fi network or any T-Mobile
If a neighboring network is causing the problem:
• Propose an informal channel usage agreement: if your neighbor
and you are both using 2.4 GHz’s channel 6, switch to 1 and 11
to increase the distance between signals. In 5 GHz, you have a
number of additional channels to choose from.
• You (and your neighbor) could move your access points farther
away from one another to reduce the signal conflict in the middle.
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TIP Another way to reduce network overlap is to engage in unilateral
or multilateral curtailment (you know, like the former Soviet Union
and the United States). You can cut the amount of transmit power
on many Wi-Fi gateways, which reduces the interference you cause.
If your neighbor backs off a little, too, both sets of network improve.
You know: the Prisoner’s Dilemma.
To reduce transmit power from an Extreme N, run AirPort Utility,
connect to the base station, and click Wireless Options in the
AirPort pane’s Wireless view. Set Transmitter Power to a level below
100 percent, click OK, click Update, and then re-test.
If Bluetooth is causing the problem:
• A Bluetooth headset from 2002 or earlier could cause terrible
interference. The standard was updated to version 1.2 in 2003,
but not all devices are upgradable. Check your equipment to see.
Set Interference Robustness
Why not use a setting labeled Interference Robustness to more
robustly resist interference and thus improve range? In short, the
setting won’t help with range but it might provide a more reliable
connection over short distances.
Apple offers Interference Robustness for 2.4 GHz use of the Extreme
N, but not for 5 GHz, which doesn’t need the additional “robustness,”
as there’s much less interference. Apple has offered the option for
years with little explanation. They describe it sketchily on their Web
site, saying that it provides better performance in the presence of
2.4 GHz cordless phones and near working microwave ovens. A writer
at Macinstruct says he figured it out: Interference Robustness
instructs the base station and Mac OS X to send packets of smaller
and smaller length to ensure that data gets through if interference
otherwise disrupts the transmission of longer sequences. Read
http://macinstruct.com/node/213 for more details.
Interference Robustness doesn’t seem to make much difference in
normal networks. One Web site documents testing that indicated that
the setting increases power while reducing reception sensitivity, thus
blasting through interference when sending data, while listening less
carefully (ignoring more noise) when receiving it.
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Turning Interference Robustness on is helpful only if you use Wi-Fi
at a short distance from a base station and if you believe that interference is causing problems. Interference Robustness reduces the range,
but can improve performance within that smaller area.
Better than using Interference Robustness, if you operate 2.4 GHz
cordless phones, you might consider switching to older 900 MHz
phones (lower quality but often better range) or newer 5.8 GHz
phones (higher price, and range is an issue); or using 5 GHz with
802.11n to avoid 2.4 GHz altogether.
You can turn on Interference Robustness in Mac OS X through the
AirPort menu in the menu bar: choose Use Interference Robustness.
Windows has no similar option in any version. For an Extreme N,
connect to your base station in AirPort Utility; click the AirPort icon,
and click Wireless; then click Wireless Options to see the checkbox.
Interference robustness can be a unilateral decision: If a single
computer or the base station has the option enabled, there could
be a performance improvement.
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Apple continues to extend itself into the media world, and the AirPort
system hasn’t been left out of the mix. When Apple introduced the
AirPort Express, they made a big deal about AirTunes, Apple’s name
for streaming music over a wired or Wi-Fi network to an AirPort
Express, which could then dump that music out as analog or optical
digital audio via a standard stereo mini-jack. Strangely, AirTunes
never appeared in any other devices.
In late 2006, Apple revealed plans to offer the Apple TV, initially
codenamed the iTV, which would stream high-definition video and
digital audio over a wired or Wi-Fi network for output via HDMI
(the high-definition digital video standard), composite analog, and
both digital and analog audio. The Apple TV was unveiled in early
2007 and shipped in March 2007.
In this section, I cover how to best configure your Apple TV to stream
video, and how to work with an AirPort Express. The big difference
between the two devices, beyond video, is that Apple TV pulls content
from connected computers, while the AirPort Express allows audio
to be pushed to it from a copy of iTunes running on a computer on
the same network.
Cheap music: The AirPort Express is still being sold as I write
this, and at $99, it’s not a bad deal for transferring audio over
your network. You can connect an Express wirelessly or via
Ethernet on an Extreme N network with no problems, except the
previously mentioned network performance hit.
Apple TV
The Apple TV can receive content from a single computer via synchronization and store it on an internal hard disk. It can also stream
content live from up to five computers on the network. The Apple TV
has 802.11n built in and can use 2.4 GHz and 5 GHz bands just like
the Extreme N. It also has just 10/100 Mbps Ethernet, not gigabit
Ethernet, which is peculiar for a device intended to move a lot of data.
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TIP If you’re using Apple TV with an 802.11g network or in the 2.4 GHz
band, connecting via Ethernet lets you sync to that one enabled
computer at the fastest possible rate. You can then disconnect from
Ethernet and use Wi-Fi thereafter. Apple has a technical note about
this: http://docs.info.apple.com/article.html?artnum=305254.
TIP Reports from Apple TV users indicate that placing an object on
top of the Apple TV can dramatically decrease the range of its Wi-Fi
radio, if you’re using Wi-Fi as your connection method.
Choose a Band
The big consideration in adding an Apple TV to your network
is ensuring that you have enough bandwidth to stream video while
performing other tasks on the network. Also, if you sync content
regularly to the Apple TV, you’ll likely want a lot of speed in order
to move your movies and audio files quickly.
MPEG4-compressed video used for top-resolution (1,080p or 1,080
by 1,920 pixels) requires about 10 Mbps of throughput. Apple says the
maximum resolution for the Apple TV is 720p, and the iTunes Store
doesn’t yet sell video at even that resolution. Thus, you need to have
somewhere between 2 and 5 Mbps of solid throughput available for
each Apple TV on a network that’s streaming video.
An ideally configured 802.11g network should top 20 Mbps in
throughput, but it’s likely to actually work at much lower speeds
due to nearby networks, interference, and other factors described
earlier. In contrast, an Extreme N network with only N devices
connected can hit 90 Mbps.
You might choose, therefore, to set up an Extreme N in the 5 GHz
band. You can read Mix Legacy, New N Networks for how to best set
this up. But, keep in mind that the speeds demanded for good video
streaming by the Apple TV might be achievable on your network at
2.4 GHz. It depends on your particular environment—and it’s worth
testing before getting rid of an older base station.
Connect an Apple TV
The Apple TV uses a straightforward way to connect to a network.
If you plug the Apple TV into an Ethernet network with DHCP
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enabled, the device automatically obtains an address. If you don’t
have an Ethernet network, or are just using Ethernet for an initial
sync, connect your Apple TV to your TV, power up both devices,
grab your Apple Remote, and follow these steps:
1. On the TV, from the Apple TV main menu, choose Setup >
2. Select Configure Wireless.
3. From the Wireless Networks screen, select your network
(Figure 58), or if your network is closed (see Closed network),
choose Other and enter a network name
Choose your network from the list.
4. If your network has an encryption key or passphrase, use the
Wireless Password screen’s visual keyboard to enter that text
(Figure 59). The Apple Remote lets you select each letter one
at a time. Select Done when finished. (The password is displayed
on the TV screen as you type it.)
5. If your network uses static addresses or has other particular
network requirements, choose Configure TCP/IP from the
Network screen to enter an IP address, set DNS servers, or control
other details (Figure 60).
With the network connected, you now can proceed to use your
Apple TV by following the instructions to pair one computer’s iTunes
library. A code appears on the Apple TV, you enter that code in that
computer’s iTunes link to the Apple TV, and then syncing begins!
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Synchronization can take some time, as noted, over a slower network.
After or instead of synchronization, you can follow instructions to
set up streaming with up to five computers on the network, similarly
using the Apple TV code paired with iTunes entry.
Use the Apple Remote to navigate the visual keyboard and select the
letters in your network passphrase.
You can set TCP/IP details manually via the Network > Configure
TCP/IP command.
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AirPort Express and AirTunes
The AirPort Express features AirTunes, a method of streaming music
from iTunes (versions 4.6 and later) through the audio output port
on the base station. You control the settings in AirPort Utility and
then play the music via iTunes.
TIP The fine folks at Rogue Amoeba offer AirFoil, a program that lets
you take the sound output from any program—not just iTunes—
and play it over AirTunes (http://rogueamoeba.com/airfoil/; $25,
downloadable demo version).
Set up music features in Airport Utility
After connecting to your base station, use the Music pane in AirPort
Utility to control music streaming and speaker settings (Figure 61).
The Music pane
lets you set
Here’s how the controls work:
• Enable AirTunes: Click this box to turn streaming on and off,
on the base station.
• Enable AirTunes over Ethernet: Check this box to let both
wired and wireless computers stream music. I can’t think of why
you might want to restrict this, but if you’re concerned about
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restricting streaming, don’t uncheck this box; instead, passwordprotect the remote speakers (see the last item in this list).
• iTunes Speaker Name: This name shows in the iTunes remote
speaker list.
• iTunes Speaker Password: Set a password to limit use of this
speaker set to people who have the password. The Verify Password
field requires you to enter the password a second time to make
sure you didn’t mistype it.
Play music with iTunes
Here are the steps for playing music via iTunes and AirPort Express:
1. In iTunes, choose File > Preferences, and then click the Advanced
icon (Figure 62).
Select Look
for Remote
with AirTunes
to automatically discover
AirTunesequipped base
2. In the General view, verify that Look for Remote Speakers
Connected with AirTunes is checked (look near the middle of the
view). This option causes iTunes to be aware of AirPort Express
Base Stations that are plugged into stereos or powered speakers.
3. If you want to control volume only from your stereo (and not also
from iTunes), select Disable iTunes Volume Control for Remote
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4. A very limited number of devices can control iTunes volume
remotely, including the Apple HiFi when connected via the
AirTunes jack on the AirPort Express. If you care about this
behavior, you can check or uncheck Allow iTunes Control from
Remote Speakers.
5. Click OK.
Now that you have a configured AirPort Express on the network
and the Look for Remote Speakers Connected with AirTunes
checkbox is selected, iTunes should display a new pop-up menu
with a speaker icon next to it in the lower right of its main window
(Figure 63).
Choose the AirPort
Express to stream
through from the pop-up
menu at the lower right.
A lock appears next to
those that are password
6. In iTunes, select a base station from the new pop-up menu.
The menu lists all the AirPort Express base stations connected
to stereos; Computer means the audio output option you chose
on your own computer in the Sound preference pane. You can
select only one item from the menu, but you can choose Multiple
Speakers to play music through both your computer and other
AirPort Express base stations as well (Figure 64).
The Remote Speakers window lets
you choose one or more speaker
sets to stream through.
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Quiet! The AirPort Express knows if there are no speakers
attached and warns you.
Here are a few more things you might like to know about AirTunes:
• Two people playing music at once: If you try to play music
through an AirPort Express that someone else is actively playing
music through, iTunes notifies you when you press the Play button
(Figure 65). If that person clicks Pause, iTunes releases that
person’s control of the speakers, and within 2–3 seconds, another
iTunes user can start playing music through that AirPort Express.
This message
appears when
someone else is
already playing
music through a
particular AirPort
• 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. When you try to connect to protected base stations to play music, you must enter the
password (Figure 66).
Connect to
passwordprotected AirPort
Express speakers
by entering the
correct password
and clicking OK.
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You can use a computer equipped with a Wi-Fi adapter card not just
as a client on a Wi-Fi network, but also as a base station. This appendix explains how to set up a software base station under Mac OS X.
Apple’s software base station has two distinct problems:
• Security: You can use only WEP encryption, which I describe
back in Use Built-in Encryption as a last-resort method of security.
It’s definitely better than nothing, however.
• Frequency: Even though 802.11n allows the use of the uncrowded
5 GHz band for less interference and better throughput, Internet
sharing over AirPort works just with the busy 2.4 GHz band.
You needn’t create an ad hoc network (also known as a computerto-computer network, an informal network that you set up quickly,
perhaps to transfer a file or to chat during a keynote speech) before
setting up a software base station, and in fact, the two are mutually
exclusive. Use an ad hoc network for connecting with another
computer when you have no Internet connection to share.
When you set up an ad hoc network by choosing Create Network
from the AirPort menu, your Mac assigns itself an IP address in
the 169.254.x.x range; Macs that connect to your network pick up
addresses in that range so they can communicate. Bonjour services
in iChat should work fine over ad hoc networks.
The Software Base Station feature is found in the Sharing preference
pane. Before starting, make sure you have either an Ethernet or an
Internal Modem connection set up in the Network preference pane,
because you can’t create a software access point without one or the
other active.
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For this example, I assume your Internet connection comes via
Ethernet from a cable modem. Here’s what to do:
1. In System Preferences, open the Sharing pane and click the
Internet button (Figure 67).
In the Internet
view of the
pane in Tiger,
you can share
your wired
as a software
base station by
choosing BuiltIn Ethernet
and checking
2. From the Share Your Connection From pop-up menu, pick either
Built-In Ethernet or Internal Modem (whichever matches how you
access the Internet), and then select AirPort in the To Computers
Using list.
3. If you want to also share a connection to wired computers
connected directly to your computer, select Built-In Ethernet from
the To Computers Using list.
Warning! Because most Macs have a single Ethernet port,
if you select Built-In Ethernet, you wind up pushing out DHCP
messages over the same network connection that you’re
retrieving your Internet feed from. This is generally not a good
idea, but might be required in some limited circumstances.
4. Click AirPort Options to set the network name, channel, and,
optionally, a WEP key (Figure 68).
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Set the wireless options you want for your software base station,
including a WEP password.
TIP If you turn on WEP and anticipate PCs or Macs without AirPort
cards ever wanting to access your network, I recommend you set
the WEP key using a dollar sign, followed by the 10-digit or 26-digit
hexadecimal key. When you type a dollar sign in a password field,
the WEP Key Length menu dims and the OK button won’t light
up until you type the correct number of matching digits in both
password fields.
5. Back in the Internet view of the Sharing preference pane, click
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I tucked the kitchen sink here at the end, because only a few of you
may be interested in the advanced features found here and there
across the AirPort Utility.
Revert to Older Firmware
Apple isn’t perfect, although many Apple fans like to pretend they’re
close to it when compared to the rest of the computer industry. Sometimes, they release software that causes their products to work more
poorly than they previously performed.
This has often happened with AirPort base station firmware, the
software code that runs on the base station itself. Many firmware
releases have turned out to have minor defects, often quickly fixed,
that disable or render erratic critical features.
Apple has neatly provided a way to go backward in AirPort Utility:
choose Base Station > Upload Firmware (Figure 69). As long as the
base station is responsive, you should be able to use this command to
restore a previous firmware release.
You can choose
firmware that’s
stored in AirPort
Utility, or choose
a separate
firmware file.
If you already have previous versions of firmware downloaded, they
appear in the Upload Version pop-up menu. Otherwise, you can
retrieve older firmware via the AirPort Utility:
• On a Mac, hold down the Option key and choose AirPort Utility >
Check for Updates.
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• Under Windows, hold down the Control key and choose File >
Check for Updates. Windows also requires that you click Show
Details to proceed.
A list of all firmware releases appears with each entry comprising
a graphic of the model type and a description of that type along with
the firmware release number (Figure 70). Select the checkbox next
to each firmware release you'd like to retrieve, and click Download.
Entries that are already stored locally are grayed out.
AirPort Utility lets you retrieve any older versions of base station
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You can also download these older firmware releases from Apple's
Web archives at http://docs.info.apple.com/article.html?
AirPort Pane
A handful of options in this view beg for additional explanation.
Base Station settings
The Set Time Automatically checkbox and field allow you to set
the time on your Extreme N (and previous models) via time servers
operated by Apple or that you specify yourself. You must choose your
time zone manually. Setting your time in this fashion can ensure that
any timed access rules you set function; see MAC address filtering.
Hardware tends to lose track of time without external correction.
Click the Base Station Options button to set blinking options. The
Status Light pop-up menu controls whether the amber/green light
on the front of the Extreme N is green when everything is situation
normal—Always On (Default)—or if it blinks with activity—Flash
On Activity.
Wireless settings
The Wireless view’s Wireless Option dialog hides several useful
controls for the built-in radio.
• Region: Choose the country in which you are operating your
Extreme N. With the Americas model, the menu lists only countries
that have approved the device. You could violate a number of laws
by setting the region to a regulatory domain in which you are not
using the base station!
• Multicast Rate: This option concerns a subset of networking
traffic that all connected computers can receive. It’s seldom used
without a particular purpose in mind, so you almost certainly
won’t need to change the value.
• WPA Group Key Timeout: On WPA-protected networks, each
connected device creates its own particular key material—based on
the WPA passphrase—in concert with an access point. Each device
also receives from the access point a group key that’s used for
broadcast traffic sent to all devices. The timeout value increases
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the entropy in encryption by ensuring that a group key doesn’t
persist for very long. It does not require that any computer log
in to the network again.
Access Control settings
The MAC Address Access Control pop-up menu lists RADIUS as
one option. If you use 802.1X or WPA/WPA2 Enterprise, here is
where you fill in server details provided by a network administrator
or a service provider you contract with.
Advanced Pane
The Advanced pane has, as you can imagine, less frequently used
Logging & SNMP settings
The Extreme N can log, or note information about, many kinds
of events, from users logging in, to updates of its internal clock, to
specific encryption information. This view controls all those aspects.
The Syslog Destination Address and Syslog Level allow an existing
system logger (a server called syslog) on a Unix or Linux—or really
any—system to receive messages from the base station, and place
them in a text file that’s updated constantly as new messages come
in. (The syslog monitor is part of Mac OS X and every Unix and Linux
flavor I’m aware of; configuring it to accept these messages requires
system administrator experience.)
The SNMP options let the base station leverage a standard method
of receiving information with a bit more sophistication than syslog.
Many network management packages use SNMP for figuring out the
status of network components and the traffic passing over them; and
determining bad behavior by users or interlopers.
If you click the Logs and Statistics button, you see additional options:
• Click Logs to see a short list of the logging messages that can be
sent to a syslog or SNMP server.
• Wireless Clients and DHCP Clients show connections and their
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Bonjour settings
Apple likes to look to the future, and the advanced Bonjour settings
are part of that forward-looking detail. In these settings, Apple lets
you set up wide-area Bonjour, a way of pushing information about
services and hardware on your local network out to the global
Internet by using the domain name system (DNS). In this scenario,
a domain name’s DNS information, which normally contains IP
addresses and mail server records, would also keep an updated list
of file servers, printers, and other Bonjour-broadcasting information
that could be accessed by people outside your local network
The problem with that? Internet service providers and DNS hosts
must support wide-area Bonjour for that to happen.
Within a large local network, such as at a college, wide-area Bonjour
can be supported internally, allowing networks of all scales to share
resources across the campus’s wide-area network. Bonjour services
on the network served by the Extreme N get shared to the next network level. Any service that uses NAT-PMP publishes information
about itself via wide-area Bonjour, if that’s enabled.
For practical purposes, and Apple has confirmed this, presently,
home users don’t need wide-area Bonjour, and most corporations
don’t have it in place. However, settings for wide-area Bonjour appear
throughout AirPort Utility.
IPv6 settings
An explanation of IPv6 could fill pages and pages, and perhaps it will
in a future edition of this book. IPv6 is the next-generation Internet
protocol that will replace the current version, IPv4, which has been
in use for decades. IPv6 was designed in the 1990s, but because it
requires a reworking of the entire infrastructure of the Internet, it’s
been slow to catch on.
IPv6 has a much larger address space, allowing trillions of addresses
compared to billions in IPv4. And, it allows address mobility: an
address in IPv4 is usually fixed to a particular router or gateway
on the Internet. With IPv6, that router or gateway can provide
forwarding info so that a mobile device can be reached elsewhere,
if desired, with no special effort.
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Some corporate networks and some ISPs in Japan now use IPv6,
which explains Apple’s support. But there’s an additional interesting
option. In IPv6, you don’t need NAT, because IPv6 addresses and
ports can be used directly. And many organizations have set up IPv6
tunnels on the Internet that allow IPv6 traffic to pass over the current
IPv4 network. The Extreme N supports this tunneling.
By default, the Extreme N is set up to allow incoming IPv6 connections and to route IPv6 traffic through these public Internet tunnels.
Because Mac OS X also, by default, enables IPv6 traffic, you do face
some exposure, and may wish to set IPv6 Mode to Link-Local Only,
which restricts traffic to the local network, and check Block Incoming
IPv6 Connections to further restrict behavior.
For the Extreme N (gigabit) Apple enhanced security options, adding
a checkbox for blocking incoming connections to the IPv6 view, and
a new view called IPv6 Firewall with configuration choices for what
IPv6 tunnels and networks can pass through.
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Leopard didn’t change the face of AirPort networking, but it did
rework how AirPort and network settings appear throughout the
system, consolidating those settings and making them more accessible. (Some long-time irritations weren’t fixed, unfortunately.)
In this special appendix, I cover three primary areas:
• The new Network preference pane, which reorganizes how you
find and configure TCP/IP and other network settings for AirPort.
• The revised AirPort menu in the system menu bar, which now
offers live information about the networks around you.
• Miscellaneous changes, ranging from Web server and printer setup
changes, to updates in mounting shared AFP and Samba volumes
in the Finder.
Watch for spots! The occasional leopard spots ( ) in the margin of this ebook can be clicked to quickly jump to corresponding
Leopard-related material in this appendix.
Meet the New Network Preference Pane
Leopard reorganized the Network preference pane to consolidate
separate activities and information into one dashboard. The Internet
Connect program is gone, replaced by features now built into the
Network preference pane. A list at the left of the pane now shows all
adapters and their respective status, replacing the previous interface
where you used different menus from the top of the pane to access
active adapters and change overall adapter settings.
Set DHCP and DHCP Client ID for AirPort
(p. 63 and p. 68)
Here are the steps to set an AirPort adapter to use DHCP to obtain
an address:
1. Open the Network preference pane.
2. Select your AirPort adapter in the list at left.
3. Click the Advanced button.
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4. Click the TCP/IP button to open the TCP/IP view (Figure 71).
DHCP settings are now found nested in the Advanced options for the
AirPort adapter, in the TCP/IP view.
5. Now, do either or both:
• Choose Using DHCP from the Configure IPv4 pop-up menu.
• Enter a name into the DHCP Client ID field to use with DHCP
reservation in AirPort Utility.
Managing Profiles
(p. 75)
To create, edit, and delete profiles in Leopard, in the Network
preference pane, select the AirPort adapter and then click the
Advanced button to see the advanced options (Figure 72).
Profiles are managed much the same as in Tiger:
• Add a profile manually by clicking the
• Delete a profile you no longer need by selecting the profile and
clicking the
• To change the preferred order in which the Mac connects to networks if more than one is available, drag a network name to a new
position in the list.
Page 168
In the Advanced options for an AirPort adapter, you can easily add,
delete, edit, and rearrange networks with which you want to connect.
• To edit an existing profile, select it and click the
button; you can
change the password or type of password, too (Figure 73).
With the edit
option, you can
change the network
name, security
type, and password
without needing
to re-select the
If you click the
button to reach the dialog shown in Figure 73,
above, you’re presented with a new option in Leopard: the Show
Networks button. This somewhat recursive seeming choice lets
you connect to a network within the edit feature, so you can change
details without exiting the nested dialog (Figure 74).
Page 169
Choose the
network from this
list, or click Other
to enter a network
from scratch.
Advanced connection options
(p. 76)
To control some aspects of how AirPort connects to networks, select
the AirPort adapter in the Network preference pane, and choose any
of the following options:
• Check Ask to Join New Networks if you want Mac OS X to alert
you when there’s no network you’ve stored a profile for in the
vicinity (Figure 75).
Warning! This feature seems to work erratically. I have never
been able to get it to work correctly and on request, but then,
out of nowhere, I’ll be prompted to join a network.
The checkbox would seem to indicate that Leopard would ask you
join networks; it rarely asks, though.
Page 170
• Click the Advanced button to reach three additional methods of
Remember Any Network This Computer Has Joined. Checked
by default, this option adds a profile for any network you join,
whether a password is required or not.
Disconnect from Any Wireless Network When Logging Out does
just that.
Require Administrator Password to Control AirPort allow you
to override someone’s attempt to switch networks or turn
AirPort off.
NOTE Apple has eliminated the set of three weird options that never
seemed to make much sense in Tiger, and that were hidden in an
Options dialog: Ask Before Joining an Open Network; Automatically
Join an Open Network; and Keep Looking for Recent Networks.
Now, the behavior is, by default, to join any network for which a
profile is stored; otherwise, Leopard asks to join a network if the
Ask To Join New Networks box is checked, which it is by default.
Joining any open network without asking is always a bad idea.
AirPort Menu
(p. 71)
The AirPort menu, a drop-down menu in the system menu bar, has
been refurbished slightly to improve how you find and connect to WiFi networks.
Dynamic network scanning
The AirPort menu is now dynamic, scanning for networks after
you hold down the mouse button to select a network (Figure 76).
Networks appear in alphabetical order, with the network that you’re
connected to coming first, if you’re connected. A lock icon appears to
the right of protected networks—ones using WEP or WPA/WPA2.
Page 171
The AirPort status line at the top
of the menu says it’s scanning
(and shows a progress spinner)
while it’s still looking for networks
after you initially hold down the
mouse button.
Network details via the Option key
In Tiger, you could hold down the Option key while clicking the
AirPort menu icon, and Mac OS X would sort the networks in order
of signal strength, from strongest to weakest.
In Leopard, however, Option-clicking the AirPort menu icon provides
details about the network (Figure 77) to which you are connected:
• The MAC address or AirPort ID of the network
• The channel the base station is using
• The signal strength measured as RSSI (Received Signal Strength
Indication), which is a relative measure of how good a signal is
• The transmit rate, which shows how fast the network link is, not
just how fast the base station can go
TIP RSSI is measured in decibels in such a fashion that a negative
number is used; -44 (minus 44), as in Figure 77 is typical. A higher
number for the RSSI therefore means less signal strength: -75 is less
power than -45.
Page 172
Option-click the Airport menu
bar icon to see network details
revealed right in the menu.
You can also reveal information about networks to which you aren’t
connected: Option-click to open the AirPort menu, and then hover
over any network in the list that you’re not connected to, in order to
see the RSSI and type of encryption, if any (Figure 78).
Option-click to
open the menu,
and then you can
hover to reveal
information about
Wi-Fi networks to
which you aren’t
Page 173
Leopard has a variety of other changes, which affect scattered
sections of the book noted below.
Finding the MAC address
(p. 59)
In Leopard, you find the MAC address of your Wi-Fi adapter by
following these steps:
1. Launch System Preferences and select the Network preference
2. Select your AirPort adapter in the list of adapters on the left side
of the pane.
3. Click the Advanced button.
The AirPort ID is found at the bottom of the AirPort view.
AirPort Utility
(p. 27)
AirPort Utility shipped as part of the Leopard set of utilities, so it no
longer needs to be installed separately from an installer disc. (Apple
also separately released a download for Tiger and for Windows
Running a Web server in Leopard
(p. 106)
Leopard no longer includes a port-based firewall that would be a
problem for running a local Web server that’s port mapped to be
reached outside the network.
The Leopard firewall, configured in the Security preference pane in
the Firewall view, automatically opens the right connections if you
enable services, such as a Web server, through the Sharing preference
pane (Figure 79).
Page 174
The Leopard firewall automatically opens ports as needed for services
enabled through the Sharing preference pane.
Add a printer in Leopard
(p. 115)
To let Leopard see a shared printer attached to an AirPort Extreme
Base Station, an AirPort Express, or a Time Capsule, follow these
1. Launch System Preferences, and select the Print & Fax preference
pane (Figure 80).
Page 175
The Print & Fax
preference pane
lets you add
and manage
2. Click the
3. Select the printer from the list that appears in the Default view
(Figure 81).
A new utility to add
printers is launched
from within the Print
& Fax preference pane.
Shared printers show
up in the Default view.
4. Click Add.
5. Optionally, choose that printer from the Default Printer list to
make it appears as the choice whenever you print.
Page 176
Accessing Shared Disks
(p. 127)
Apple seems to have abandoned the AirPort Disk Utility (p. 128–130),
part of the initial package of software that was installed with AirPort
Utility, for managing disks mounted via an AirPort Extreme Base
Station. Instead, Leopard manages the base station server and disks
through the Finder, just like any other network volume.
In any Finder window, you now see a list of servers in the new Shared
category in the sidebar (Figure 82). This list shows any servers on
the local network with AFP or Samba volumes available for mounting,
as well as FTP servers that use Bonjour to advertise their availability.
The Shared section of the sidebar shows available servers. If you
select a server and enter its password, volumes appear at the right.
The “Connected as” banner at the top shows the user name you’re
connected as. Click Disconnect to unmount all volumes for the
selected server.
To mount a volume from one of these servers, follow these steps:
1. Select the server name under Shared in the sidebar.
2. Now:
• To connect as a Guest user, you needn’t do anything for this
step. Leopard automatically tries to connect using the Guest
login, and it then shows any volumes that can be mounted in
that fashion.
Page 177
• To use a named account, click the Connect As button in the
upper right and enter your credentials. Leopard is clever
enough that for AirPort Extreme and Time Capsule shared
drives that use just a password for access—no user accounts
being defined—to prompt you just for that password.
3. Double click a volume that’s shown in the mounted server window
to mount it on your system.
By default, Leopard doesn’t show a mounted server on the actual
Desktop as an icon. This can be confusing! To fix this oversight,
follow these steps:
1. Choose Finder > Preferences
2. Click General.
3. Under “Show these items on the Desktop,” check Connected
Interference robust enough
(p. 148)
The setting for Interference Robustness, a way to improve reception
for a wonky AirPort connection, is no longer available in Leopard.
This setting can still be set for 2.4 GHz networks via AirPort Utility
for AirPort Extreme, AirPort Express, and Time Capsule, but it’s gone
from Mac OS X. We were never sure if it helped much, anyway!
Software Base Station
(p. 158–160)
Much to everyone’s chagrin, Apple just moved the location of its software base station controls; they didn’t improve those controls at all.
Instead of being found in the Sharing preference pane’s Internet
view, which no longer exists, network sharing is a service listed in the
Sharing preference pane. Open the pane and click Internet Sharing
to see the option. If you choose AirPort from the Share Connect from
pop-up menu, you can then click the AirPort Options button to set
the same choices as the last two releases of Mac OS X: 2.4 GHz only
(despite 5 GHz networks being available, faster, and less in use), and
WEP encryption only (despite WPA’s far superior quality).
Page 178
In contrast to traditional print books, Take Control books offer clickable links, full-text searching, and free minor updates. We hope you
find them both useful and enjoyable to read.
About the Author
Glenn Fleishman contributes
regularly to Macworld, the New
York Times, the Economist, Popular
Science, and the Seattle Times. He’s
the Macintosh columnist for the
Seattle Times, and a contributing
editor at TidBITS.
Glenn spends much of his time
writing about wireless networking.
He co-wrote Take Control of Your
Wi-Fi Security with Adam Engst,
and he edits the daily Web log
Wi-Fi Networking News
(http://www.wifinetnews.com/) and five related wireless blogs.
Glenn also appears weekly on KUOW-FM in Seattle to talk about
technology (http://kuow.org/).
He lives in Seattle in a bungalow with his wife and two sons. His
oldest’s first word was “book,” not “Mac.”
The new edition of this book happened fast—Apple shipped the
Extreme N, and I and the Take Control team was determined to get
out a fully revised edition of the previous book—fast!
I must thank Tonya Engst for her tireless and rapid work in editing;
Adam Engst, a long-time friend, colleague, and collaborator, also
deserves thanks for his role in fostering and perpetuating my work
on Wi-Fi and AirPort. More thanks to Dan Frakes for his feedback
and insight into early Extreme N troubles and fixes; the Take Control
authors who have been fantastically supportive; and to a host of Take
Page 179
Control pre-release technical reviewers, notably Criss Hyde, Chris
Pepper, and Rich Wolfson. Thanks to Jeff Carlson for the use of his
Apple TV screen photos.
Thanks are also due to Apple Computer’s Teresa Brewer for her help
in sorting out some early Extreme N quirks, and relaying my technical
quibbles and bug reports to the AirPort team, notably Jai Chulani and
John Richey.
Great thanks go to my wife, Lynn, who accepted a few weeks of me
sitting on a couch every night tapping away, while our second child
gestated. Sure, I’m working, honey, sure!
Thanks to Robert F. Unger for pointing us to the great tip on downloading older firmware releases for base stations.
About the Publisher
Publishers Adam and Tonya Engst have been
creating Mac-related content since they
started the online newsletter TidBITS, in
1990. In TidBITS, you can find the latest
Macintosh news, plus read reviews, opinions, and more
Adam and Tonya are known in the Mac world
as writers, editors, and speakers. They are also
parents to Tristan, who thinks ebooks about clipper
ships and castles would be cool.
Production Credits
Link-making AppleScript: Matt Neuburg
List macros and leopard spots ( ): Sharon Zardetto
Take Control logo: Jeff Tolbert
Editor in Chief: Tonya Engst
Publisher: Adam Engst
Special thanks this time go to Amelia and Oliver Habicht, for helping
with bicycles, and to Andrew and Monique Nielsen, for being fun and
relaxing guests.
Page 180
Take Control of Your
802.11n AirPort Extreme Network
ISBN 1-933671-28-9
April 2008. Version 1.2
Copyright © 2008 Glenn Fleishman. All rights reserved.
TidBITS Publishing Inc.
50 Hickory Road
Ithaca, NY 14850 USA
TAKE CONTROL books help readers regain a measure of control in an oftentimes out-ofcontrol universe. Take Control books also streamline the publication process so that
information about quickly changing technical topics can be published while it’s still relevant
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