Viewing debug counters for one MST instance

The show spanning-tree debug-counters instance command allows you to display the aggregate values of all MSTP debug counters maintained on a switch for a specified spanning tree instance. These aggregate values are a summary of information collected from all ports that have VLANs assigned to the specified instance.

Use this command to troubleshoot the global MSTP diagnostic information displayed in show spanning-tree debug-counters command output when you suspect unauthorized MSTP activity in a specific MST instance.


show spanning-tree debug-counters instance instance-id

Displays debug counters for MSTP activity on all ports configured for VLANs in the specified MST instance.

The valid values for instance instance-id are 0 to 16, where 0 specifies the default MST (CIST) instance and 1 to 16 specify a multiple spanning tree (MST) instance.

Viewing bug counters for a CIST instance

The following example shows sample output of the show spanning-tree debug-counters instance command when applied to the Common and Internal Spanning Tree (CIST) instance (default MST instance 0) in the network.
switch(config)# show spanning-tree debug-counters instance 0

 Status and Counters - CIST Common Debug Counters Information

  MST Instance ID : 0

  Counter Name                      Aggregated Value Collected From
  --------------------------------- ---------------- -------------- 
  Invalid BPDUs                     0                Ports
  Errant BPDUs                      172603           Ports
  MST Config Error BPDUs            0                Ports 
  Looped-back BPDUs                 0                Ports 
  Starved BPDUs                     0                Ports 
  Exceeded Max Age BPDUs            0                Ports 
  Exceeded Max Hops BPDUs           0                Ports 
  Topology Changes Detected         1                Ports 
  Topology Changes Tx               3                Ports 
  Topology Changes Rx               2                Ports 
  Topology Change ACKs Tx           0                Ports 
  Topology Change ACKs Rx           0                Ports 
  TCN BPDUs Tx                      0                Ports 
  TCN BPDUs Rx                      0                Ports 
  CFG BPDUs Tx                      0                Ports 
  CFG BPDUs Rx                      0                Ports 
  RST BPDUs Tx                      0                Ports 
  RST BPDUs Rx                      0                Ports 
  MST BPDUs Tx                      5                Ports 
  MST BPDUs Rx                      172577           Ports