Figure 5-13 shows the Motorola SB4200 cable modem popularly used to connect to
residential broadband services. Many users have
ADSL/DSL modems instead of cable; some
users even have satellite Internet access. Regardless of whether you
use cable, ADSL/DSL, or satellite, you should have a device (such as
the cable modem shown in Figure 5-13) with flashing
lights and an Ethernet port that provides you with Internet access.
You may have bought this device in a computer store or directly from
your ISP, or perhaps you rent it from your ISP.
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Some ISPs may have supplied you with a device that uses a USB
connection to your computer instead of Ethernet, or even a card that
was installed inside your computer. To connect your broadband service
to a wireless network, you'll need an external
device with an Ethernet port. You may need to contact your
ISP's technical support, explain what you are trying
to do (give them the simplest version of the story:
you're trying to connect a wireless access point to
your broadband service), and request the correct device. If your ISP
refuses to help or doesn't understand your request,
it is time to find a new ISP.
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A common limit of broadband connections is
that only one computer can be connected to the Internet at any one
time. As discussed in Chapter 2, there are many
ways the ISP can impose the restriction, such as MAC address locking,
or issuing a single IP
address to the cable modem. So to enable multiple computers to
wirelessly access the Internet, you could use a wireless router. (See
DHCP and NAT earlier in
this chapter for information on how DHCP and NAT features found in
wireless routers work around this limitation.) One such wireless
router is the Linksys BEFW11S4 802.11b
Wireless Access Point with 4-port switch (see Figure 5-14).
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In most cases, this limit is a practical limitation dictated by the
scarcity of IP
addresses. Most ISPs permit you to use a router to get around this
restriction, and some will happily sell you a router and may also
send a technician to your home to set it up (often for an extra fee,
but this is sometimes included with the purchase of a router).
However, in some cases, your ISP's Terms of Service
(TOS) may contractually limit you to one computer, in which case they
will typically charge you a nominal fee for each additional computer
to which you connect. If so, then using a router is a violation of
the TOS. This was more common during the early days of broadband;
nowadays, most ISPs don't care how many computers
you connect, as long as they are your computers and you
aren't sharing your connection with the rest of your
neighborhood.
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Figure 5-15 shows one possible configuration for a
home network.
See Section 5.4, later in this
chapter, for information on setting up and configuring the BEFW11S4.