Am 10.01.2010 15:33, schrieb David Hláčik:

Hello I will briefly draw the situation

[ ... ]

Please help,

Thank you in advance.

David

The router runs CentOS or Fedora? Because you are sending your mails to both mailing lists.

Alexander

On Sun, Jan 10, 2010 at 6:33 AM, David Hláčik david@hlacik.eu wrote:

Hello I will briefly draw the situation

Router with one interface eth0 , to local network 10.123.0.0/16

on a local network ADSL modem with IP  10.123.10.11

I want to use 10.123.10.11 as a connection to internet .

Because of that I have created default route "ip route add default via 10.123.10.11 dev eth0"

I do not want my ADSL modem to do NATing , since it shows to be slow. I have configured static route on ADSL modem "10.123.0.0/16 via 10.123.10.11" which ensures traffic comming from internet will ge to my router.

Now i want to configure NATTING. My concern is, how to create iptables rule which will match only the traffic going via 10.123.10.11 and only for this will make SNAT. If I will do iptables -A POSTROUTING -o eth0 --j SNAT --to-source 213.194.242.198 this will not work . I need to add there a magic words that only traffic going via 10.123.10.11 should be SNATted.

Unless the machine running iptables has a NIC with a IP address of 213.194.242.198 I don't believe it's possible with ipchains.

The MODEM is the interface between 213.x and 10.y networks.

If you created a DMZ by moving your LAN to say the 192.z network (or a different 10.y network) then you should be able to get it work with 2 NICS in the ipchain machine.

In this case, you would route between the 10 network and the 192 network with 2 NICs and SNAT the 10 network.

The WAN would be the 213.x network, the DMZ would be 10.y, and the LAN would be the 192.z network.