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Date: Tue, 3 Jun 2003 10:36:20 -0400 (EDT)
From: Matthew George <mdg@secureworks.net>
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To: Paulo Roberto <nirv199@yahoo.com>
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Subject: Re: Packet flow through IPFW+IPF+IPNAT ?
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On Mon, 2 Jun 2003, Paulo Roberto wrote:

> --- Fernando Gleiser <fgleiser@cactus.fi.uba.ar> wrote:
> > On Mon, 2 Jun 2003, Vlad GALU wrote:
> > Or, in other words, IPF always 'sees' the real IPs, not the NATed
> > ones.
>
> Is it also true for IPFW? Does the rules apply always to the real
> addresses instead of the natted ones? So why does the "divert natd"
> rule must be the first rule in ipfw? (in rc.firewall it is rule 00050).
> Is the packet reinserted on the queue, or it just wait a "pass" rule so
> it can be put on rule #00050 and go on?
>
> TIA
>
> Paulo Roberto
>

It depends on where the divert rule is.  If it's the first rule, then yes.
You can do pre-nat filtering by placing rules before the divert if you
want.  I typically do all my RFC1918 et al. filtering on my external
interfaces pre-nat.

-- 
Matthew George
SecureWorks Technical Operations