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Date:      Thu, 21 Nov 2002 16:04:28 +0100 (CET)
From:      "Patrick M. Hausen" <hausen@punkt.de>
To:        David Kelly <dkelly@hiwaay.net>
Cc:        "Patrick M. Hausen" <hausen@punkt.de>, Helge Oldach <freebsd-stable-21nov02@oldach.net>, archie@dellroad.org, guido@gvr.org, sullrich@CRE8.COM, greg.panula@dolaninformation.com, FreeBSD-stable@FreeBSD.ORG
Subject:   Re: IPsec/gif VPN tunnel packets on wrong NIC in ipfw? SOLUTION AND QUESTIONS
Message-ID:  <200211211504.gALF4Sej086710@hugo10.ka.punkt.de>
In-Reply-To: <20021121145332.GA57883@grumpy.dyndns.org>

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Hi!

> Glad I didn't know this in advance as that is exactly what I believe I
> have. Two FreeBSD systems, one on each end connected to cable modem.
> About 8 machines behind one on 192.168.100.0/24 and 10 or 15 behind the
> other on 10.0.0.0/24. An ESP tunnel between.

;-)

> Other than my decrypted packets have started appearing to ipfw as if
> they were coming from fxp1 (which is what started this mess) everything
> else is working just fine.

It is only filtering the decrypted packets that I'm talking about
all the time. It's impossible to build a filter that says:

- ESP from my peer is OK
- 10... to 192.168... is OK if it's coming out of the ESP tunnel
- 10... to 192.168... is _not_ OK if it's coming in my external IF
  in plain text

If you want to allow the derypted traffic in, you have to allow all
traffic with identical addresses, even if it hasn't arrived
through the ESP tunnel but just came to the outside IF of your
network by some other route. 

Regards,

Patrick M. Hausen
Technical Director
-- 
punkt.de GmbH         Internet - Dienstleistungen - Beratung
Scheffelstr. 17 a     Tel. 0721 9109 -0 Fax: -100
76135 Karlsruhe       http://punkt.de

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