This book tells you how to build your own network. Unusually, it explains why you'd want to do things, not just how. It starts with a simple 2-machine network and goes on to a full network connected to the Internet, with a firewall and internal routers, and DNS and email servers. It explains the software tools you need to understand how your network operates. It includes practical troubleshooting and diagnostic techniques that you can apply just about everywhere, so you can solve problems in your own network and in systems configured by others. And it assumes things will go wrong - nothing works first time! - so it explains the common error messages and tells you how to fix them. It ties together the various networking components so you view your network as a whole, not just disjointed pieces. It can be used as the basics for a course of self-study or a taught training course. (It is widely used as a university and college text for networking courses.) This is a reprint of the original 2003 edition.