IPTables again: selective NAT?

IPTables again: selective NAT?

am 11.03.2005 21:25:52 von Jens Knoell

Is it possible to selectively enable NAT? i.e. I want to NAT everything
from 192.168.0.0/24 and nothing from 192.168.1.0/24 ...?

Thanks
J
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Re: IPTables again: selective NAT?

am 11.03.2005 22:44:07 von GrantC

On Fri, 11 Mar 2005 13:25:52 -0700, you wrote:

>Is it possible to selectively enable NAT? i.e. I want to NAT everything
>from 192.168.0.0/24 and nothing from 192.168.1.0/24 ...?

Yes, anything is possible, clarify your query please.

Cheers,
Grant.
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Re: IPTables again: selective NAT?

am 11.03.2005 22:44:21 von Andreas Unterkircher

What about:

iptables -t nat -A POSTROUTING -s 192.168.0.0/24 -j SNAT --to yourIP

iptables -t nat -A POSTROUTING -j DROP
or
iptables -t nat -P POSTROUTING DROP

Andreas

Jens Knoell wrote:

> Is it possible to selectively enable NAT? i.e. I want to NAT
> everything from 192.168.0.0/24 and nothing from 192.168.1.0/24 ...?
>
> Thanks
> J
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
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>
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Re: IPTables again: selective NAT?

am 11.03.2005 23:16:14 von Jens Knoell

Andreas Unterkircher wrote:

> Jens Knoell wrote:
>
>> Is it possible to selectively enable NAT? i.e. I want to NAT
>> everything from 192.168.0.0/24 and nothing from 192.168.1.0/24 ...?
>>
>> Thanks
>> J
>> -
>> To unsubscribe from this list: send the line "unsubscribe
>> linux-admin" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
> What about:
>
> iptables -t nat -A POSTROUTING -s 192.168.0.0/24 -j SNAT --to yourIP
>
> iptables -t nat -A POSTROUTING -j DROP
> or
> iptables -t nat -P POSTROUTING DROP
>
> Andreas

I don't quite think that'll do the job... so as requested, a clarification:

The network layout is like this:
eth0 is hooked up to the LAN and has a private IP (say, 10.0.0.1)
eth1 is hooked up to the DMZ and has a public IP (say, 12.13.14.15)

There's an IPsec gateway running on this machine for connecting outlying
offices to the central office.

The machine does NAT connections to the outside world. Then there are
the IPsec connections... and that's what's giving me headaches:

If an IPsec client connects to the server at 12.13.14.15, it connects
the remote LAN to the office LAN. As an example, lets say I have an
office in NYC which connects to my central office, say in Utah.
So:
Utah server has WAN 12.13.14.15, Utah LAN has 10.0.0.1/24
NYC IPsec router has 44.33.22.11, NYC LAN has 192.168.0.1/27

When the IPsec connection establishes, the routing table automatically
adds the necessary entries. I can ping from NYC to Utah, but NOT from
Utah to NYC.

The lines responsible for NAT are:
# Enable NAT
/usr/sbin/iptables -t nat -A POSTROUTING -o eth1 -j SNAT --to-source
12.13.14.15
# Allow NAT from inside only
/usr/sbin/iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
/usr/sbin/iptables -A INPUT -m state --state NEW -i ! eth1 -j ACCEPT
/usr/sbin/iptables -A INPUT -m state --state NEW -i eth1 -j REJECT

As best as I can tell, the packages from the Utah server to the NYC
router get NAT'ed at least by the Utah server. Which I am trying to
explicitly avoid. If I throw out the first line from above, things work
just fine. Since the NYC router has a static IP I figured I just disable
NAT for anything going to 44.33.22.11 and should be done with it. Except
that I cannot figure out how to do that :/

Does that make sense?

J
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