On Fri, 2013-01-11 at 16:13 +0100, Paweł Brodacki wrote:
2013/1/9 Alan Cox <alan(a)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!"