Hi all My small cable ISP has a Linux box which is supposed to route my ip addtress. Normally, he is issuing private space ips in address range 172.16.x.x. I have asked for a live IP and he has issued one, 202.x.x.139. The problem is that he has other IP addresses on the same interface, which are NATted to provide connectivity to 172.16.x.x. So when I get a web request, my server logs 202.x.x.137 as the source IP, which is actually my gateway on the ISP machine. On the other hand when I send mail, my source ip from the other end looks to be 202.x.x.130, which is again the ISPs IP. It seems that despite being issued a live IP, my IP is being proxied somehow or the source address is being mangled. The ISP does not seem to have the expertise to route the IP properly ;-) and has told me either to accept it, to tell him how is he supposed to do it or go back to 172.16.x.x address. I myself am a ipfilter newbie. Can someone tell me how an IP is routed on an interface which is providing NAT services on a second IP. Pointers to resources for further reading on issues involved and any similar scripts/samples will be greatly appreciated. (My ISP seems to talk about pre-routing a lot....does not really tell exactly how he is pre-routing the packets for my IP). With best regards. Sanjay.
