After power cycle on system the line drivers for the network interface seemed to die, no link connection and no light. This is a mother board interface and dmesg still shows hardware discovery. Bought a PCI Express card and installed it. Then modified the mac address in the /etc/sysconfig/networking-scripts/ifcfg-xxxx file. Still no joy. Noticed that the dev name changed so I move the file to match the new dev name and edited the device name in the file. Still no joy. Was only able to ping the interface ip address. Next I modified the /etc/nsswitch.conf file to not use dns. Then I can ping the host name and localhost. Disabled IPV6 as it seemed to becausing problems, probably something to do with the auto generated address, just a guess. Checked netstat -r and it is correct. Network still does not work. Not able to ping to another system on the local link. If I try an "ip link show" it wedges the system. I get messages about CPU's stalling. This initially had me thinking something else was wrong with the mother board but after sever more hours of investigation the system seems fine except for the lack of a functioning network link. I'm wondering if at some level, it is still trying to access the failed interface since it is known by the hardware discovery. There is no BIOS setting to disable the interface.