Chapter 2. Issues of TCP/IP Networking

Table of Contents
Networking Interfaces
IP Addresses
Address Resolution
IP Routing
The Internet Control Message Protocol
Resolving Host Names

In this chapter we turn to the configuration decisions you'll need to make when connecting your Linux machine to a TCP/IP network, including dealing with IP addresses, hostnames, and routing issues. This chapter gives you the background you need in order to understand what your setup requires, while the next chapters cover the tools you will use.

To learn more about TCP/IP and the reasons behind it, refer to the three-volume set Internetworking with TCP/IP, by Douglas R. Comer (Prentice Hall). For a more detailed guide to managing a TCP/IP network, see TCP/IP Network Administration by Craig Hunt (O'Reilly).

Networking Interfaces

To hide the diversity of equipment that may be used in a networking environment, TCP/IP defines an abstract interface through which the hardware is accessed. This interface offers a set of operations that is the same for all types of hardware and basically deals with sending and receiving packets.

For each peripheral networking device, a corresponding interface has to be present in the kernel. For example, Ethernet interfaces in Linux are called by such names as eth0 and eth1; PPP (discussed in Chapter 8 ) interfaces are named ppp0 and ppp1; and FDDI interfaces are given names like fddi0 and fddi1. These interface names are used for configuration purposes when you want to specify a particular physical device in a configuration command, and they have no meaning beyond this use.

Before being used by TCP/IP networking, an interface must be assigned an IP address that serves as its identification when communicating with the rest of the world. This address is different from the interface name mentioned previously; if you compare an interface to a door, the address is like the nameplate pinned on it.

Other device parameters may be set, like the maximum size of datagrams that can be processed by a particular piece of hardware, which is referred to as Maximum Transfer Unit (MTU). Other attributes will be introduced later. Fortunately, most attributes have sensible defaults.