Re: DAD question

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> > Globally unique. The point here is that the Ethernet standards require
> > a globally unique MAC address *per box*, not necessarily per interface.
> > The "Sun way" of storing a MAC address in EEPROM and configuring all
> > network cards with the same MAC address was perfectly compliant, just
> > somewhat unusual.
> 
> But that's not the whole story, right?
> 
> The only way this can work is if one assumes that each interface of that box is connected to a different IP subnet. I don't even think Ethernet rules are what matters here. If the box should happen to be dual homed to the same IP subnet, that Sun scheme doesn't work. (I suppose unless only one of the box's interface is active at any given time.

Obviously. And I believe more modern Sun boxes actually have a MAC
address per interface. All I'm saying is that there is nothing wrong,
standards-wise, in having *one* globally unique MAC address per box.

Having the same MAC address shared between two (or more) boxes *is*
wrong, standards-wise. And unfortunately that's exactly what we're
seeing in practice. Not often, but "often enough" that it may not be
safe to ignore the possibility.

Steinar Haug, Nethelp consulting, [e-mail]