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# Configuring TCP/IP Networking

In this chapter, we will go through all the steps necessary to setting up TCP/IP networking on your machine. Starting with the assignment of IP-addresses, we will slowly work our way through the configuration of TCP/IP network interfaces, and introduce a few tools that come quite handy when hunting down problems with your network installation.

Most of the tasks covered in this chapter you will generally have to do only once. Afterwards, you have to touch most configuration files only when adding a new system to your network, or when you reconfigure your system entirely. Some of the commands used to configure TCP/IP, however, have to be executed each time the system is booted. This is usually done by invoking them from the system /etc/rc scripts.

Commonly, the network-specific part of this procedure is contained in a script called rc.net or rc.inet. Sometimes, you will also see two scripts named rc.inet1 and rc.inet2, where the former initializes the kernel part of networking, while the latter starts basic networking services and applications. Throughout the following, I will adhere to the latter concept.

Below, I will discuss the actions performed by rc.inet1, while applications will be covered in later chapters. After finishing this chapter, you should have established a sequence of commands that properly configure TCP/IP networking on your computer. You should then replace any sample commands in rc.inet1 with your commands, make sure rc.inet1 is executed at startup time, and reboot your machine. The networking rc scripts that come along with your favorite distribution should give you a good example.

- Setting up the proc Filesystem
- Installing the Binaries
- Another Example
- Setting the Hostname
- Assigning IP-Addresses
- Writing hosts and networks Files
- Interface Configuration for IP
  - The Loopback Interface
  - Ethernet Interfaces
  - Routing through a Gateway
  - Configuring a Gateway
  - The PLIP Interface
  - The SLIP and PPP Interface
  - The Dummy Interface
- All About ifconfig
- Checking with netstat
  - Displaying the Routing Table
  - Displaying Interface Statistics
  - Displaying Connections
- Checking the ARP Tables
- The Future