> If you read the Ethernet spec really carefully
> (this is a very-little known feature), you'll find that Ethernet
> addresses only have to be _host_ unique, thus explicitly allowing a
> multi-homed host to give all its interfaces the same MAC address.

That is correct.  I like the idea of sharing the ethernet address
between ports as Sun does. It has one benefit: the file /etc/ethers
can only support one ethernet address per hostname. This might help in
some baroque diskless booting situations.

It has one problem that I know of: You cannot put two ethernet cards
(from one machine) onto the same ethernet wire. You might want to for
fault tolerance reasons (though there are routing issues which might
cause you problems).

> Note that giving multiple interfaces on the same wire the same address
> probably won't work too well. :-)  I'm not sure that this case was
> ever considered, because (in a way) it really doesn't make that much
> sense, unless you're trying to run multiple protocol stacks that
> can't share an interface, which is arguably a software problem.

You do not want to put two ethernet cards onto the same ethernet cable
for performance reasons -- it actually lowers performance because
(theoretically) it increases collisions.