problems with two NICs

slackwarefan · 10-28-2006, 10:17 PM

I'm trying to set up a sort of a proxy server router using the new Slackware distro and iptables.

I have two NICs in the computer, one going to the router, and the other going to my windows laptop.

I've gotten Linux to get an IP from the router, and to give an IP to the windows laptop. I can ping from the linux machine to the windows laptop using

ping -I eth0 192.168.*.*

However I cannot do this any other way. I cannot ping the linux machine from the windows machine and I cannot access any of the network services (telnet etc) on the linux machine from the windows machine. If I run iptraf on linux while I try to ping or telnet to the box from the laptop, I can see the connection attempts, but linux isn't responding. I can get linux to respond to pings if I have it ping itself on eth0 from eth0, but windows doesn't get a response from eth0. Why?

I'm guessing that the network services are only running on eth1, the NIC hooked up to the internet which I'm using as my external nic, but I dont' know how to get them to run on the other one as well.

Thanks in advance everyone.

blackhole54 · 10-30-2006, 04:35 AM

Quote:

Originally Posted by slackwarefan

I'm guessing that the network services are only running on eth1, ...

If you can ping out through eth0, then eth0 must be running. I am guessing you have a firewall issue.

slackwarefan · 10-30-2006, 10:41 PM

I've cleared the iptables rules but it still happens, how else could this be related to firewalls?

I'm thinking now that it's because I'm not using a patch cable but I'm just using a regular network cable from the PC to the laptop. This would explain it, but I can still ping one way, and I can still assign DHCP addresses, would this still be a plausible explaination?

blackhole54 · 10-30-2006, 11:58 PM

Quote:

Originally Posted by slackwarefan

I've cleared the iptables rules but it still happens, how else could this be related to firewalls?

If you've cleared all of the tables (including nat and mangle, just to be thorough) then the firewall is not an issue.

Quote:

I'm thinking now that it's because I'm not using a patch cable but I'm just using a regular network cable from the PC to the laptop. This would explain it, but I can still ping one way, and I can still assign DHCP addresses, would this still be a plausible explaination?

I thought "patch cable" and "regular network cable" were the same thing. (I've been wrong before

) In any case, you should use a crossover cable to directly connect two computers together. If you are not but you are still getting partial functionality, I don't know what to say; I've seen mysterious (to me) things before! But if you're not using the correct cable I would say it is definitely a plausible explanation for your problems!

(BTW, I've not fully understood the inner workings of ethernet since it ceased being a single coax cable that connected everything together!)