[cisco-voip] Switch STP problem

[Gordon Smith]

Hi Kevin,

I've seen weird behaviour with 7940 phones on 2950 switches before,
which could be the same problem you're seeing.
The problem is caused by the phone sending BPDU's to the switch, which
then puts the port into ERR-DISABLED state.

Try adding into your port config this:
Spanning-tree bpdufilter enable

This blocks all BPDU's in and out of the switchport - it's worked well
for me

Cheers,
Gordon



> All,
> 
> We have a problem with STP convergance.  We have a gigabit 
> switched network, using a combination of 3500, 3550, 3560 
> switches.  We use the below switch config.  According to 
> Cisco documentation, spanning-tree port fast is susposed to 
> prevent the voice vlan port from participating in STP.  We 
> even put bpduguard on the port.  We tested the config and 
> switches up stream still re-converge all the way up to the 
> CORE, when a IP phone is unplugged.
> 
> Interface fa 0/2
> switchport mode trunk
> switchport trunk encapsulation dot1q
> switchport voice vlan XXX
> switchport trunk native vlan XX
> spanning-tree portfast
> spanning-tree bpduguard enable
> 
> 
> --
> 1LT Knowlen, Kevin