Re: duplicate MAC addresses

["John Stoffel" <john@stoffel.org>]

>>>>> "marty" = marty  <marty@goodoldmarty.com> writes:

marty> Greg KH wrote:
>> > On Tue, Aug 18, 2009 at 04:27:04PM -0400, marty wrote:
>>> >> I got trouble...
>>> >> (duplicate MAC addresses)
>> >
>> > That's a bug in your hardware, have you asked your manufacturer to
>> > resolve this for you?  That violates the ethernet spec...

marty> I have resolved that problem as of today. I found this was
marty> caused by the software I had been using. If a hardware issue
marty> remains, it is moot.

marty> The bonding driver/utilities normally sets the bond address to
marty> the MAC of the first NIC. But it also set the MAC of the slave
marty> (eth3) to the MAC of the first NIC. This persists through
marty> reboots so that is how my MACs got duplicated.

marty> Resetting the MAC corrected those problems and everything works
marty> fine now.

Doesn't this point to a udev rules problem?  What should happen if
there are conflicting devices which both satisfy a condition, but
where only one device is allowed to match?

Now I realize that with MAC addresses you're actually allowed to have
multiple NICs on a host all with the SAME Mac addr, but only if
they're on different segments.  Older Sun boxes all used to have a
single MAC address across all ports.  This usually isn't a problem
since the ethernet spec says that MAC addresses are local to the
segment, and with switches and bridges, the segment is is limited.

Fails when you have bonding drivers and other HA tricks which I'm not
up on though.  

John