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Date:      Wed, 2 Oct 2002 08:16:23 -0700
From:      Luigi Rizzo <rizzo@icir.org>
To:        "Daniel C. Sobral" <dcs@tcoip.com.br>
Cc:        Georg Graf <georg-ipfw@graf.priv.at>, freebsd-ipfw@FreeBSD.ORG
Subject:   Re: Natd plus statefull connections impossible?
Message-ID:  <20021002081623.B23060@iguana.icir.org>
In-Reply-To: <3D9B0B6F.5020304@tcoip.com.br>; from dcs@tcoip.com.br on Wed, Oct 02, 2002 at 12:06:23PM -0300
References:  <20021002115143.GA54827@graf.priv.at> <3D9B0B6F.5020304@tcoip.com.br>

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On Wed, Oct 02, 2002 at 12:06:23PM -0300, Daniel C. Sobral wrote:
...
> For a long time, I also thought it was not possible. But, while working 
> on another firewall, and trying to understand how NAT interacted with 
> firewall rules (they were separated), it came to me that all rules 
> applied to the real addresses, never their translation.

Actually, the last statement is not true in general (it
may be true with the specific rule organization that Daniel
suggests below.)
In general, the addresses that the firewall sees depends on whether
the packet is checked before or after the packet is reinjected in the
firewall after going through the natd daemon.

	cheers
	luigi

> 
> Requirements:
> 
> 1) If the packet is outgoing (ie, will be natted on it's way out), you 
> want the NAT to be the last thing done.
> 
> 2) If the packet is incoming (ie, will be "un-natted" on it's way in), 
> you want the NAT to be the first thing done.
...

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