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Date:      Tue, 15 Apr 2003 18:49:46 -0700
From:      <chris.ahlers@mail-space.net>
To:        <freebsd-ipfw@freebsd.org>
Subject:   IPFW/NATD: Client behind firewall connecting to server behind firewall AS IF it were really EXTERNAL
Message-ID:  <000001c303ba$75cc27a0$3401a8c0@neptune>

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I have successfully implemented NAT w/ dynamic rules on my firewall, and
have a question about a SPECIAL case that I would like to implement.

Everything works for external (internet) hosts coming in to my internal
(NAT-ed, behind firewall) webserver.
Everything works for my client pc's to access the internet, etc.

I will spare everybody the typical and predictable rulesets that
everybody uses in common, instead I will only give the relevant
information for the discussion.

firewall external IP = a.a.a.15  (internet ip address)
firewall internal IP = b.b.b.254 (private ip address)

NATD: alias_address = a.a.a.15
NATD: redirect_port tcp b.b.b.100:80 80
NATD: deny_incoming

webserver internal IP = b.b.b.100
example client pc IP = b.b.b.57
client pc gateway IP = b.b.b.254 (firewall)

QUESTION:

So, EXTERNAL hosts will connect to a.a.a.15 to connect to my webserver,
and the nat/redirect happens just fine.
However, INTERNAL hosts are unable to connect to my webserver via
a.a.a.15 (since this is not actually the webserver's address).

How can I get an internal host to connect to my internal webserver as if
the webserver were actually at the external IP?

BEFORE anybody starts recommending that I simply just point the internal
host directly at the internal webserver 

OR 

that I change my DNS config to have an inside view, etc., I would like
to point out that my $75 linksys router will do EXACTLY what I am asking
for automatically.

It seems that when the internal client pc attempts to connect I have to
NAT the external webserver IP to the INTERNAL IP, then NAT & connect on
behalf of the client pc.

Any suggestions?

C_Ahlers
code-space.com








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