Random MAC address - why?

Berserker · 9 Oct 2010 at 11:52

MAC addresses are supposed to be fixed, right? Well not in my case. I kept getting new network adapters appear every time I rebooted my laptop and sat down to investigate last night.

Turns out that every time I reboot, the MAC address of my wired network adapter changes.

I've eliminated all driver and OS-related issues (PXE boot handily displays the MAC address, so there's not even an OS loaded at that point).

Anyone got any ideas?

System: Asus UL30A. Chipset: Atheros AR8132

tolien · 9 Oct 2010 at 14:45

Dodgy BIOS battery? They're not really as fixed as claimed but obviously it shouldn't be changing when you reboot.

Berserker · 10 Oct 2010 at 12:34

Well, the system BIOS settings (inc. RTC) are fine, so that battery is good.

I wouldn't mind so much if it didn't keep forgetting network settings because it's considered a new adapter. Having 20+ defunct network adapters probably isn't a good idea either.

I could get around most of it in Linux with some udev magic, but no such luck in Windows.

J.B · 10 Oct 2010 at 15:56

Very odd. Is there any similiarity to the MACs? Im thinking specifically about the first 6 digits which identifies the manufacturer. I've never seen anything like that before.

When you do a PXE boot is the MAC different each time there as well?

Berserker · 11 Oct 2010 at 13:19

Yes, there is similarity. Seems to be one of 64K addresses - i.e. xx:xx:00:00:xx:xx through xx:xx:FF:FF:xx:xx.

MAC address does indeed follow this pattern during PXE boot.

I've found a few other reports of this with ASUS and/or Gigabyte boards. Something to do with them being assigned an invalid MAC. I don't recall this machine doing this when it was new, however.

J.B · 11 Oct 2010 at 13:55

Very odd, the only thing I could think ofis a faulty controller chip on the motherboard.

If you have a spare tenner and PCI port its probably worth picking up a new NIC as the easiest solution.

Berserker · 11 Oct 2010 at 13:57

It's a laptop.

I'm thinking of RMA-ing it, but want to make sure it's not something stupid I've done (to avoid the dreaded 'no fault' RMA).

J.B · 11 Oct 2010 at 18:36

Ahh, if its covered under warranty then Id deff send it back. Thats got to be a hardware fault.

Berserker · 11 Oct 2010 at 19:02

OK - if I'm well enough then it goes back tomorrow.

I've got a brand new Vertex 2E to go in it so better it's RMA'd before I do that.