How to Set/Get UUID for a NIC

Mike Chambers mike at mtchambers.com
Fri Jan 11 16:19:23 UTC 2013


On Fri, 2013-01-11 at 16:13 +0100, Paweł Brodacki wrote:
> 2013/1/9 Alan Cox <alan at lxorguk.ukuu.org.uk>:
> > 
> > They are supposed to be unique *per machine* - you can have two nics on
> > the same machine with the same MAC although this is rare.
> >
> > Alan
> 
> Alan, please, verify information before dissemination.
> MAC address assigned to a physical NIC ought to be globally unique.
> Ethernet frames are sent to MAC address, so two identical addresses
> present in any broadcast domain would awfully confuse network
> switches. See e.g. Wikipedia article on MAC
> https://en.wikipedia.org/wiki/MAC_address. Hardware producers reserve
> prefixes (first 3 bytes of the address) and are responsible for not
> manufacturing devices with identical suffixes (last 3 bytes of the
> address).


>  This should result in globally unique MAC addresses, however
> I did encounter NICs with identical ones (cheap stuff of unknown and
> dubious provenance).

You try to call out Alan, THEN your last sentence above, states exactly
what Alan said, they *can* have identical in the same machine *BUT
RARE*.  And you just stated you encountered it once?  Sounds like what
he stated to me.


-- 
Mike Chambers
Madisonville, KY

"Best little town on Earth!"



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