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How to enable the Spanning Tree Protocol debugs in Catalyst 6000/6500 Switches that run the Cisco IOS system software


Enable the logging of Spanning Tree Protocol (STP) events on the bridges and switches of the network that experience the failure when you cannot precisely identify the source of the problem or if the problem is transient. If you want to limit the number of devices to configure, at least enable this logging on devices that host blocked ports as the transition of a blocked port is what creates a loop.

In order to debug spanning tree activities, use the debug spanning-tree command.

Note: Use the remote login switch command in order to access the switch console or a specific module and then enter debug spanning-tree events. The debug command also possibly increases the CPU utilization.

Refer to the Log STP Events on Devices That Host Blocked Ports section of Spanning Tree Protocol Problems and Related Design Considerations for more information.