Multiple Instance Spanning-Tree Operation

Troubleshooting an MSTP Configuration

Displaying 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 the show spanning-tree debug-counters instance 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.

Syntax: show spanning-tree debug-counters instance <instance-id>

This command 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 from 0 to 16:

0 specifies the default MST (CIST) instance.

1 to 16 specify a multiple spanning-tree (MST) 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. For a description of each counter, refer to Table 4-1 on page 4-66.

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