In itself, a topology change notification is not a bad thing, but as a good network administrator, it is better to know their origin in order to be sure that they are not related to a real problem. Identifying the bridge that issued the topology change is not an easy task. However, it is not technically complex.
Most bridges only count the number of TCNs they have issued or received. The Catalyst 4500/4000, 5500/5000, and 6500/6000 are able to show the port and the ID of the bridge that sent the last topology change they received. Starting from the root, it is then possible to go downstream to the initiator bridge. Refer to the show spantree statisticscommand for more information.
There is no command show spantree statistics in Catalyst 4500