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From: John Madden <jmadden@ivytech.edu>
To: Grant Taylor <gtaylor@riverviewtech.net>
Cc: Mail List - Netfilter <netfilter@vger.kernel.org>
Subject: Re: "DNAT" w/o changing source address?
Date: Thu, 04 Oct 2007 09:14:02 -0400	[thread overview]
Message-ID: <1191503642.13379.12.camel@localhost.localdomain> (raw)
In-Reply-To: <47042728.1060508@riverviewtech.net>

> Um, correct me if I'm wrong, but Destination NATing should not alter the 
> source IP address of the packet that is being NATed.
> 
> Honestly, I wonder how you are doing your DNATing and if you are not 
> also possibly unknowingly SNATing as well.

Hmm, well here are the rules I'm running.  The port forward:

echo "1" > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A PREROUTING -d $EXTIP -p tcp --dport 25 -j DNAT --to
$MAILSERVER:25

And the SNAT for return traffic:

iptables -t nat -A POSTROUTING -d $MAILSERVER -j SNAT --to $EXTIP

...At least, I found that traffic wouldn't flow without this additional
rule.  Have I gotten something else fundamentally wrong here?

John



-- 
John Madden
Sr. UNIX Systems Engineer
Ivy Tech Community College of Indiana
jmadden@ivytech.edu


  parent reply	other threads:[~2007-10-04 13:14 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-10-03 15:21 "DNAT" w/o changing source address? John Madden
2007-10-03 23:35 ` Grant Taylor
2007-10-03 23:50   ` Pascal Hambourg
2007-10-04  1:17     ` Grant Taylor
2007-10-04 13:14     ` John Madden
2007-10-04 13:14   ` John Madden [this message]
2007-10-04 14:09     ` Grant Taylor
2007-10-04 14:19       ` John Madden
2007-10-04 15:13         ` Grant Taylor
2007-10-04 14:17     ` Pascal Hambourg
2007-10-04 14:22       ` John Madden
2007-10-04 14:59         ` Pascal Hambourg
2007-10-04 15:13           ` John Madden
2007-10-04 15:29             ` Grant Taylor
2007-10-04 19:33               ` Grant Taylor
2007-10-04 16:01             ` Pascal Hambourg
2007-10-04 15:23           ` Grant Taylor
2007-10-04 15:52             ` Pascal Hambourg
2007-10-04 19:12               ` Grant Taylor
2007-10-04 19:25                 ` John Madden

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