* SNAT rule on LAN - unexpected result
@ 2013-07-21 8:51 Al Grant
2013-07-22 5:31 ` Vigneswaran R
0 siblings, 1 reply; 2+ messages in thread
From: Al Grant @ 2013-07-21 8:51 UTC (permalink / raw)
To: netfilter
Hi All,
Doing a little experimenting with iptables and more specifically SNAT.
I have two computers, a Ubunutu box and a Win7 box with a switch between them.
On the Ubuntu box (192.168.15.200) I have added:
iptables -t nat -A POSTROUTING -o eth4 -j SNAT --to-source 192.168.15.201
Now I run wireshark on the Win7 machine and various bits of broadcast
traffic which was coming from .200 now shows as from .201 - great!
So I tried a ping from the Win7 machine and would expect a reply to
show in wireshark, but that the src address be changed to .201 - but
nope I get a reply from .200. How is this so?
Conversely a ping from the Ubuntu machine to the win7 machine shows
the packets with a src of .201 in wireshark - as expected.
Cheers in advance,
-Al
--
"Beat it punk!"
- Clint Eastwood
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: SNAT rule on LAN - unexpected result
2013-07-21 8:51 SNAT rule on LAN - unexpected result Al Grant
@ 2013-07-22 5:31 ` Vigneswaran R
0 siblings, 0 replies; 2+ messages in thread
From: Vigneswaran R @ 2013-07-22 5:31 UTC (permalink / raw)
To: Al Grant; +Cc: netfilter
On 07/21/2013 02:21 PM, Al Grant wrote:
> Hi All,
>
> Doing a little experimenting with iptables and more specifically SNAT.
>
> I have two computers, a Ubunutu box and a Win7 box with a switch between them.
>
> On the Ubuntu box (192.168.15.200) I have added:
>
> iptables -t nat -A POSTROUTING -o eth4 -j SNAT --to-source 192.168.15.201
>
>
> Now I run wireshark on the Win7 machine and various bits of broadcast
> traffic which was coming from .200 now shows as from .201 - great!
>
> So I tried a ping from the Win7 machine and would expect a reply to
> show in wireshark, but that the src address be changed to .201 - but
> nope I get a reply from .200. How is this so?
> Conversely a ping from the Ubuntu machine to the win7 machine shows
> the packets with a src of .201 in wireshark - as expected.
I think, this is due to the fact that 'nat' table will be consulted only
for new connections. Unlike ping request, the ping *reply* may not be
considered as part of a new connection.
Regards,
Vignesh
^ permalink raw reply [flat|nested] 2+ messages in thread
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2013-07-21 8:51 SNAT rule on LAN - unexpected result Al Grant
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