STP Topology Changes

[Thomas Yarger]

All,

I'm experiencing some oddities with STP on my network. I run the sh spanning-tree detail | inc from|exec|changes on my STP Root Bridge and I'm seeing A LOT of topology changes on a couple of my VLAN's. Here is an example...

 VLAN0160 is executing the rstp compatible Spanning Tree protocol
  Number of topology changes 14411 last change occurred 00:11:38 ago
          from GigabitEthernet2/13

First, I want to make sure I'm interpreting this output correctly. The output is stating there was 14411 changes 11 minutes ago? Is this value reset after an interval of time? How often is this polled?

Second, the VLAN's that are seeing this kind of activity are geographically dispersed but connect to same VPLS, Metro-E WAN. Could that cause anything? I know this type of WAN is viewed as one broadcast domain but I have everything segemented real well and nothing "bleeds" over to another location.

Lastly, What would cause this amount of topology changes? What would be "normal" in a stable network? What would be the best way to approach this to find the root cause?

Thanks!
 

[glen.grant]

This is telling you who caused it last and it g2/13 .  Whats on that port ?  If its just user on the port do you have portfast turned on ?  If it's not then that will cause a topology change everytime the user goes on and off the network.  In a normal stable network you should see very few . Make sure all the user ports  are configured correctly across your switches.