STP issues

[mazheralam]

I am running with 4 core switches of 6509 with fibre connectivity having two different sites. Each site is having two core routers.One site ( A ) does have CISCO IOS version and does not have any problem but other side (B) running with CAT-os has huge problem. Suddenly the whole site got down for a minute or two and then it come normal. It happens in not a specific time, Just random. Can any one give me any suggestion to find the problem or resolve the issue.

[nate-miller]

I can't remember my CatOS syntax exactly, but:

Look at the details for that spanning tree instance. See wehre your spanning tree events are coming from- which port. Track it down to the port and see what's connected there.

Make sure servers are in portfast, switches and multiple uplinks aren't in portfast mode, etc. DOn't turn off STP. DOnt' enable bptu filter on a per-interface basis.

Is it all one big VLAN, or multiple VLANs per site? Does just one VLAN go down, or the entire site? What is CPU load like on the switch during the outage?