From mboxrd@z Thu Jan  1 00:00:00 1970
From: Nils Juergens <ju@isf.rwth-aachen.de>
Subject: Re: Port forward to public IP's behind firewall
Date: Fri, 05 Sep 2003 09:04:58 +0200
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On Thu, 04.09.03, Gareth Hastings <Gareth.Hastings@netcall.com> wrote:

> firewall have public addresses. Now I would like to add a port forward rule
> that sends all incoming mail to another IP address. I am not sure what I'd
> need to do. I didn't think SNAT or DNAT were needed here as no NAT is
> happening. Anyone have any ideas? Do I need to mangle the destination
> address?

If you send packets to another IP address why exactly is that not DNAT?

Try:

iptables -t nat -A PREROUTING -p tcp -d $fw_ip --dport 25 -j DNAT --to $target:25

cya,

Nils