What kernel version are you running?
Do you have the network card drivers as modules or compiled directly in?
Where are you trying to ping the linux box from? A hub? Are both cards connected to the hub? Do either of them respond?
Are you specifying the kernel modules to use?
What's the output of ifconfig?
What distro are you running?

j

>My problem is that as soon as I add a second ethernet card I can no longer ping the Linux server. I am using a Realtek 8129 and a 3c509. The 3c509 I plan to hook to my DSL and the 8129 to the internal network. For the sake of the experiment I used addresses 192.168.174.107 & 108 respectively to set the cards up. If I only have one card (eth0) installed everything works. As soon as I install the second card (eth1) I can no longer ping the server. When Linux boots both cards check [OK].