How to fix "Device eth0 has different MAC address than expected, ignoring."
 

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.

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.