TCP/IP works with a wide variety of networks. TCP/IP cannot make assumptions about the network it runs on - the network interface and its characteristics must be identified to TCP/IP. In this chapter we have looked at several examples of how to configure the physical network interface over which TCP/IP runs.
ifconfig is the most commonly used interface configuration command. It assigns the interface its IP address, sets the subnet mask, sets the broadcast address, and performs several other functions.
TCP/IP can also run over telephone lines using dial-up connections. Two protocols are available to do this: Serial Line IP (SLIP) and Point-to-Point Protocol (PPP). PPP is the preferred choice. It is an Internet standard and offers better reliability, performance, and security.
There are several steps to setting up a PPP or a SLIP connection: selecting and configuring the serial protocol, configuring the port and modem, making the dial-up connection, and completing the remote login. Some programs, such as dip, combine all of these steps into one program. Other programs, such as pppd and chat, separate the functions.
Configuring the network interface allows us to talk to the local network, while configuring routing allows us to talk to the world. We touched on routing in Chapter 2 and again in this chapter in our discussion of routing metrics for ifconfig and default routes for PPP and SLIP. In the next chapter we look at routing in much greater detail.