If your talking about doing static NAT go see:
Read the first paragraph. If you want to use the Fast NAT kernel option, you
will need to download the IPROUTE2 package. It works fine, but had
difficulties to make it work with ipchains water marks.
Usualy, the help for a kernel option will tell you what you need and where
to get it.
> Are there any docs on NAT for linux?
> I havent found any howto's or mini's.
> Its in the TOC of the Net-4 Howto but it isnt actually in the document I
> got from sunsite.
> Andrew E. Troup