Problem with SNAT

Jason Opperisano opie at
Thu Sep 2 22:17:51 CEST 2004

On Thu, 2004-09-02 at 14:57, Bgs wrote:
>   Greetings,
> I have problems with the following setup:
> A linux with two NICs. One with IP of and one with
> I have DNAT-ed traffic coming in on the that was originally 
> sent to (Another node doing the DNAT). I have problems on the 
> route back so I decided to SNAT the backward udp traffic to  soource 
> and send the SNATed packets back on another route.
> I added the line to nat postrouting (-d target_net -s -p udp -j 
> SNAT --to-source but the packages don't even seem to hit the 
> nat postrouting chain. Let alone my SNAT rule.
> Any ideas what could be wrong ?
> Thanks
> Bgs

since i have to guess (hint:  post your rules [1] if you want us to find
the problem for you)...

i would say that your filter rules drop the packet before they ever get
to the POSTROUTING chain of the nat table.


[1] - iptables -vnL && iptables -t nat -vnL && iptables -t mangle -vnL

Jason Opperisano <opie at>

More information about the netfilter mailing list