[c-nsp] protecting router MAC addresses

Marko Milivojevic markom at pangalactic.net
Wed Oct 13 07:31:46 EDT 2004

> We do have spanning tree enabled on all vlans.  We don't have bpduguard
> enabled & that sounds like something worth doing.  But I don't know if
> enabling bpduguard would prevent the problem or not - we haven't been able
> to recreate the problem.  By "daisy chained" I mean
> switch == phone == phone == phone
> so spanning tree shouldn't make any difference since there's no loop

    A little bit uncharted territory for me, but... Are you *sure* there is 
no loop? Even if there is no physical loop (which looks like there is, based 
on log entries you posted earlier), are you 100% sure that internal switch 
in Cisco phones is supposed to be able to handle topology you have? I am not 
so sure about it. They are relatively braindead bridges, as far as I 
understand them (do they even support STP?). If the end of chain is 
connected to another switch port, I can easily see the loop forming.


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