networking

Flakey BIOS in Gigabyte GA-M68SM-S2L Makes MAC Address Change on Reboot

Over the weekend I have been setting my new Mythbuntu pair, a split. back end and front end. Everything has gone pretty smoothly.

One issue I did hit was the onboard NIC on my Gigabyte GA-M68SM-S2L motherboard despite what the specs say it is a "nVidia Corporation Unknown device 054c (rev a2)" which uses the forcedeth driver. Everytime I rebooted the box the NIC would increment its interface number - eth0, eth1 ... eth6 and so on. Changing the "Smart LAN" setting in the BIOS from auto to disabled just disables the NIC, not what I wanted.

After googling I discovered that others had experienced similar problems with ASUS boards with nVidia NICs, changing their MAC addresses. Looks like Gigabyte (and ASUS) have been shipping invalid MAC addresses on some of their boards, and forcedeth isn't happy about it, so it just generates a new (valid yet) random MAC address.

With a little help from sysfs I was able to hack my udev config so it all works now. My /etc/udev/rules.d/70-persistent-net.rules looks like

SUBSYSTEM=="net", DRIVERS=="forcedeth", ATTRS{vendor}=="0x10de", ATTRS{device}=="0x054c", NAME="eth0"

I grabbed the output of "cat /sys/class/net/ethX/device/{device,vendor}" to populate the relevant ATTRS entries above.

I am not sure what you do if you have 2 onboard NICs and they are both broken.

Gigabyte (and ASUS) or nVidia should look at fixing their broken kit to save people from wasting time on this.

Update: It turns out it was a dodgy driver shipped by Ubuntu