I have a network which consists mainly of Catalyst switches (a Catalyst 4510 as the root) sprinkled also with a number of small business switches (SG300 switches). I am investigating TCN alerts as it seems when there is a topology change our VMware infrastructure sends out an alert. Our network is running RSTP across all our switches however whilst all the Catalyst switches on the network are in synch with when a topology change took place on the main Vlan. The small business switches are totally out of synch regarding topology changes on the network. I would expect all the switches to be totally in synch with each other. Am I correct ??? what can I do to modify this as it is restricting me locating what ports may cause a topology change. Thanks Simon.