[c-nsp] per interface Mac-Address on a switch

[sthaug at nethelp.no]

> > > can any one tell me why cisco use a mac-address per interface on a
> > switch?
> > > Is there a document, which explains this? If i look on different switch
> > vendors, i see mostly only 1 mac-Address per switch.
> > 
> > MAC address per port is required for spanning tree.
> Why needs it a mac per interface?
> Do you have a link for it? I haven't found it on the cisco site.

Actually each port needs a *port ID* - this is part of the spanning
tree tie-breaker algorithm. But a base MAC address for the switch and
a port ID leads naturally to a MAC address per port.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no