MAC Addresses

philjayj · 6 Oct 2009 at 22:33

Just a quick and simple question: Is every MAC/node address in the world unique?

Thanks

paradigm · 6 Oct 2009 at 22:42

Werewolf · 7 Oct 2009 at 00:18

paradigm said:
Yes.

I think that's a yes in theory...IIRC you can clone mac addresses, and i've got vague memories of one manufacturer releasing a batch of NIC's where they'd messed up setting the MAC addresses in the factory (I think they did the whole batch with the same MAC address rather than it going up by one for each card).

So to all practical intents and purposes it should be unique (and has to be to work properly on the same network/internet), in reality not always.

At least as I understand it

Dewotter · 7 Oct 2009 at 00:28

You definately can clone/spoof mac addresses. Many machines have this ability using software like Broadcom Tools and Intel ProSet utilities.

Dist · 7 Oct 2009 at 00:41

The MAC address on the hardware should always be unique. But at system boot that MAC address is copied into RAM, then anything that needs to use the address just looks at the RAM instead of looking at the NICs hardware all the time. This means that all you need to do to change what the system/network thinks your MAC address is, is simply edit its value stored in RAM.

J.B · 8 Oct 2009 at 10:11

You might also like to know that the first 6 figures in a MAC address are unique to each manufacturer.

List can be found here: http://standards.ieee.org/regauth/oui/oui.txt

philjayj · 8 Oct 2009 at 13:48

Thanks for all the info, much appreciated.