Understanding Network Address Translation

Network Address Translation (NAT) allows you to hide a group of computers (such as a network) behind one IP address. In the Unix world, this is known as IP masquerading. Basically, your network sits behind the NAT server, which also is typically a proxy server and/or firewall. This means that you only need one "legal" IP address for the server running the NAT software. The IP addressing scheme that you use on the computer network behind the NAT server is really up to you (although there are ranges of IP addresses reserved for this purpose, which we will discuss in a moment).

The Internet connection sharing service provided by Windows Me, Windows 2000, and Windows XP (discussed earlier in the chapter) is really an example of the use of NAT. Windows 2000 Server also offers a full-blown version of the NAT service as part of its Remote Access and Routing features.