Just re-install linux on new system and replaced nic card. Restarted and getting this message: "Device eth0 has different MAC address than expected, ignoring."

That sounds like udev.

Do a:

It will probably show you a file that has a udev rewrite rule for the eth0 and has the mac hardcoded. More than likely in the file /etc/udev/rules.d/60-net.rules

---------- Post added 02-19-13 at 04:37 PM ----------

This could also be ignored if it is infact udev and the nic is working as intended.

If it isn't your udev rules its the /etc/sysconfig/network-scripts/ifcfg-eth0(red hat) or /etc/sysconfig/interfaces(debian) that has the MAC address hardcoded. If the network daemon trys to start eth0 and the MAC doesnt match the config file it wont start.

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Based on my understanding of the problem statement:

The MAC address that the card has ( as read by the system at boot ) is different from the MAC address the file in /etc/sysconfig/network-scripts/ifcfg-<device> ( RHEL ) says it is.

dmesg | grep eth ---will give you network devices and their MAC address
OR
dmesg | more --- the system will have read every device and called it out at boot


Fix ( edit / replace ) the MAC address value in the relevant interface file in /etc/sysconfig/network-scripts/ifcfg-* with that that the system says it is in dmesg and up the interface or restart the network service.

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