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Date:      Thu, 21 Nov 2002 09:37:04 +0100 (CET)
From:      Helge Oldach <freebsd-stable-21nov02@oldach.net>
To:        hausen@punkt.de (Patrick M. Hausen)
Cc:        archie@dellroad.org, guido@gvr.org, dkelly@HiWAAY.net, 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:  <200211210837.gAL8b4Se080747@sep.oldach.net>
In-Reply-To: <200211200820.gAK8Ki6G041336@hugo10.ka.punkt.de> from "Patrick M. Hausen" at "Nov 20, 2002  9:20:44 am"

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Patrick M. Hausen:
> One question to Guido: why would it be necessary to add a new
> device - be it called esp0 or fxp_esp0 or similar - to tag the
> packets as coming from? Can't the decrypted packets just come
> from the already existing gif0 tunnel interface?

Essentially because you don't need to use a gif interface at all if
you implement ESP tunnel mode. The only purpose for gif is to get the
routing straight, which is: You have a route to the remote inside
network via the gif interface, and you have a "public" route via the
real interface.

You can as well implement this by placing the internal route to an IP
address which has a static ARP entry with the MAC address of the public
default gateway. Been there, it works.

Again compared to Cisco IOS, it's even simpler there, as you can create
"remote routes" which avoids fiddling with MAC entries, e.g.

! remote (public) via our default gateway
ip route 62.12.34.56 255.255.255.255 194.123.123.124
! remote (internal)
ip route 172.16.0.0 255.255.0.0 62.12.34.56

(Note that this isn't possible with the BSD stack. It would simplify
things it it would...)

The core problem is that we have a single routing table only, and hence
we have a mix of internal and public routes. Consequently we will see
both internal and external packets on interfaces. Therefore I don't see
the need for an extra interface. I regard the gif set-up as confusion
already, because this interface isn't used at all.

Specifically, a beast such as esp0 would only work for ESP tunnel
mode, but again add confusion for ESP transport mode and AH. (What IP
addresses do you assign the esp0 interface in transport mode?)

Finally, such an implementation would be quite unique in the industry. I
would prefer to keep reference to existing implementations.

Helge

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