Hello! We are currently trying to build a packet filtering firewall using SUSE Linux 6.2 and ipchains. The hardware used is a Pentium 133 with two Level One NICs using the Realtek 8139 chipset.
From what we read in the literature (Firewall and Ipchains HowTo, several articles in the german magazine ct etc.) it seemed quite manageable, but then reality struck.
After several successless tests with a bigger installation we set up an installation almost identical to the one shown in part 6.3 of the "Firewall and Proxy Server HOWTO" written by Mark Grennan, the only difference being the IP-adresses for the outside part. Our setup passes all the tests described except one - it doesn't forward. I can ping any computer from the firewall/router, I can ping both sides of the firewall from the LAN, but I can only ping the outside adress from the outside and I can't get through it. IP-forwarding is switched on and all default policies in ipchains are set to ACCEPT. We are quite desperate (and my boss is losing patience), so any ideas are highly welcome. Might it be useful to try some other network adapters? Is there something we have overlooked? Is there a fault in the HOWTO? Best regards