[geeks] Re: [SunRescue] Help!

[Greg A. Woods]

[ On Wednesday, April 18, 2001 at 22:25:31 (-0500), Bill Bradford wrote: ]
> Subject: [SunRescue] Help!
>
> Can someone point me to a good, *NON-LINUX-HOWTO* page that
> explains what IP masquerading is, what its used for, and 
> advantages?

Well what the Linux dudes call "IP Masquerading" is really generally
called Network Address Translation, or NAT by the rest of the world.
There is also "Port and Address Translation", somtimes referred to as
PAT, though may people lump NAT and PAT together under the common name
"NAT", or sometimes "NPAT" for Network and Port Address Translation.
(None of this should be confused with an Application Layer Gateway, or
ALG, aka proxy, either of course!  :-)  So, if you search for "NAT
network address translation" in Google you'll get about 61,400 links.  :-)

There are probably lots of Cisco documents describing NATs since IOS
includes one since about 11.x or so IIRC.  I've found Cisco docs to be
generally good enough to learn from even if you're not going to use a
Cisco to do the implementation (though perhaps that's because I do have
some familiarity with their systems in general).

The canonical freeware NAT/PAT is part of Darren Reed's excellent IP
Filter package (even HP have bundled it into HP/UX 11.00, and it works
well with SunOS-4 & SunOS-5, IRIX-6.2, and some versions of Linux, not
to mention being an integrated part of all *BSDs too):

	http://cheops.anu.edu.au/~avalon/ip-filter.html

There's some excellent documentation on his pages, including a diagram
of how IP Filter and its NAT/PAT fit into the kernel, as well as in the
"Other Links" section, particularly:

	http://www.obfuscation.org/ipf/ipf-howto.txt

This latter link is probably what you're looking for, though the main IP
Filter page has a diagram off one of the first links.

A quick read through this one suggests it's quite easy to understand and
accurate too:

	http://www.vicomsoft.com/knowledge/reference/nat.html

A real zero-brainer (written by Cisco! :-) is here:

	http://www.howstuffworks.com/nat.htm

-- 
							Greg A. Woods

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