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Date:      Mon, 2 Dec 1996 09:45:44 -0700 (MST)
From:      Nate Williams <nate@mt.sri.com>
To:        hackers@freebsd.org
Subject:   Routing questions
Message-ID:  <199612021645.JAA28732@rocky.mt.sri.com>

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Background:
I've got a block of 32 IP addresses assigned to me (a chunk out of a
class C), and everything has been working wonderfully thanks to advice
from folks on hackers when I set this up.

Howevever, my boss now wants his own little dedicated network at home.
Currently, he's got a single line he dials into on demand and using PPP
and arp he can have one of the home computers dial-in and be 'on the
net' which works well.  Each of his machines has it's own dedicated IP
addresses, and we've setup MX records so that email and such go to the
correct places when they are down.

But,   now  he wants  to  buy  a simply little   gateway  box that has a
dedicated link and then have 3 machines sit behind it on the ethernet at
home and I have *no* idea how to setup the routing for it.  We've got
the IP addresses to spare, but we can't afford to break out current
office network into two chunks (we can have more than 15 hosts in the
office active at any one time), and I'd also like to set something up
like this at home as well.

I've thought of two solutions, and the first is so ugly I'm not even
sure it's doable.  Basically, I would create host routes to all of his
machines on my 'gateway' box that point to his home-router box.
However, how does his home router box know how to route packets from his
internal ethernet vs. over the PPP line to our office ethernet?  There
is also the problem of the portable boxes needing two separate ethernet
addresses (or a scrip that deletes the host routes), one for home and
one for the office.

The other solution is to do some sort of address munging on my gateway
box.  Basically, I'd assign him one of the RFC 1918 networks, and then
have a mapping of 'fake' IP to 'real' IP address on my gateway box.
This would seem to be a fairly common 'firewall' type of job, but I'm
not familiar if such code exists for FreeBSD, or if someone has a better
solution.

If anyone has any good advice that is fairly simple to implement I'm all
ears!


Nate



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