5.2 Case Study: The Home Network

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.

Figure 5-13. The Motorola SB4200 cable modem

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.

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).

Figure 5-14. The Linksys BEFW11SE Wireless Access Point with 4-port switch (802.11b)

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.

Figure 5-15 shows one possible configuration for a home network.

Figure 5-15. The configuration of a home network

See Section 5.4, later in this chapter, for information on setting up and configuring the BEFW11S4.