I have a network based on 3com switches, with a switch 5500G in the core and switch 4500 and 4400 on the edge. I have some problems with stability in the network and I have started to dig into spanning tree-related issues. When I view the STP-statistics on the coreswitch I can see that the topology in the network changes quite often (by using the "display stp"-command), even if I have not changed anything in the network. No switches are shut down and no swithes are added. It seems the the switch logs a topology change many times every dag, in fact several times per hour. My question is: How can I determine what is causing to topology change? Probably a link on a switch in the network is flapping up and down and causing the event, but how to find it? Any tips?