I installed 2 nic cards in my pentium 4 computer running rhel5 to be used as a proxy server and connect 2 computers in each network card for testing . The problem is I cannot ping or use the 2 cards simultaneously . One must be deactivated for the other to be ping . The Network configuration panel indicate both card status as active but i can only ping the first to be activated . I have already set onboot=yes to both cards but still the same result after restarting . The nic cards are onboard - Realtek RTL8139 and pci -3com 3c905b. Any Suggestion pls.

Welcome to LQ!

You can have multiple NIC cards and use them simultaneously. You have to be careful with the configuration, though, and it sounds like you may have created a conflict with your configuration. A machine can only have one default gateway and if both NIC have a default gateway assigned you will see the symptom you describe.

Please post the output of the iconfig command. BTW, please either attach it as a text file to your reply or place it between code tags. Your network configuration file may also be helpful in suggesting a solution to your problem. This may be located in /etc/network/interfaces, but this is distribution dependent.

i assume that one nic is connected to the LAN and the other to WAN.so each NIC must have it's own ip subnet. and just like Noway2 said,i assume that you're getting a conflict because of your ip configuration .

Give the output of and I think you are in conflict with multiple interface. I also had with 3 NICs.

The 2 nic have the same subnet .Changing the subnet of 1 card solved the problem . Thanks