Welcome, gentle reader.
You are about to delve into the fascinating (and sometimes horrid) world of NAT: Network Address Translation, and this HOWTO is going to be your somewhat accurate guide to the 2.4 Linux Kernel and beyond.
In Linux 2.4, an infrastructure for mangling packets was introduced, called `netfilter'. A layer on top of this provides NAT, completely reimplemented from previous kernels.
(C) 2000 Paul `Rusty' Russell. Licensed under the GNU GPL.