[c-nsp] protecting router MAC addresses

Marko Milivojevic markom at pangalactic.net
Wed Oct 13 06:47:58 EDT 2004

> We've had a couple of times recently where Cisco IP phones daisy-chained
> together get into a state where they echo frames back to the switch.  Once
> that happens the switch learns the router MAC address on the user port &
> traffic meant for the router is black-holed.  It finally happened on a
> switch running 5.x code & we got a lot of these syslog messages

    Isn't this is sort of a problem that spanning tree is designed to solve? 
Enabling spanning tree or bpduguard on your access ports should solve the 
problem I think... if I understood well what you meant by "daisy chained" IP 


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