From: Pascal Hambourg <pascal.mail@plouf.fr.eu.org>
To: Mail List - Netfilter <netfilter@lists.netfilter.org>
Subject: Re: IPTables NAT: Strange behaviour: bug?
Date: Wed, 25 Apr 2007 00:26:48 +0200 [thread overview]
Message-ID: <462E8428.6080502@plouf.fr.eu.org> (raw)
In-Reply-To: <462DC260.5090206@gmail.com>
Hello,
Pedro Gonçalves a écrit :
>
> In attachment you can find an capture made at the machine with IPTables,
> in which you can see:
> -packets 1 and 2: Packet going from the client behind NAT
> (175.16.0.1:10000) to Stun Server (192.168.2.164:3478) -> Client's
> public address is 192.168.2.159:10000
> -packets 21 e 22: Packet going from the client behind NAT
> (175.16.0.1:10000) to the other NAT's public addr
> (192.168.2.173:20000)-> Client's public address is 192.168.2.159:1029
>
> Why is the client getting different NAT mappings?
The NAT mechanism may change the source port in order to avoid a clash -
or at least what it considers a clash - with an existing mapping (same
external source and destination addresses and ports). I guess that this
existing mapping was created by packet #17 received from the other NAT
device : 192.168.2.173.20000 -> 192.168.2.159.10000.
A possible workaround may be to DROP or REJECT this incoming packet in
the INPUT table, so the associated connection tracking and NAT mapping
are deleted.
next prev parent reply other threads:[~2007-04-24 22:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-24 8:40 IPTables NAT: Strange behaviour: bug? Pedro Gonçalves
2007-04-24 22:26 ` Pascal Hambourg [this message]
-- strict thread matches above, loose matches on Subject: below --
2007-04-23 19:22 Pedro Gonçalves
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