Hi U are not getting the problem. When A sends echo request packet to B, B should send a reply packet back to A. But this is not what's happening. I have put a sniffer on B. B is receiving the packet as such with source as A and destination B. SO what u r saying that i am chaanging the ip b4 forwarding the packet is not happening. The problem is :B is sending the ICMP packet with Source:B Destination :Gateway's Interface to B The ICMP packet type is Destination unreachable and it's code is Protocol Unreachable. The same thing also happens the other way round i.e when B pings to A. So i assume problem is somewhere in the code..Can it be some port problem or what???? __________________________________________________ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/