Does anyone have a good method for tracking down the origin of spanning tree topology changes in a network of primarily 3500XL switches? The core switches are 6000s and they identify the port that the last TCN was received on. The only TCN info I can find on 3500XLs is the number received. Even on 3560 switches I see only see the TCN count and how long ago it was received. Is there a debug command that will log this info? debug spanning events perhaps?