On Sun, Jan 10, 2010 at 6:33 AM, David Hláčik <david at 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. -- Enjoy global warming while it lasts.