I have the following rule in my firewall: iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE And that's the only rule if postrouting chain. It's working fine but from time to time a packet leaves the server with the original ip and not with the server's. It's happening like 1 "wrong" packet for 100 or 200 ok. I've tried in other servers with same results and different "Mandrakes" ( 9.1, 10,1 and 2006.0 ). And different cpus ( p3, p4, amd, all with 512 mb ram ). Any ideias ? Thanks a lot Leandro