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Multiple Instance Spanning-Tree Operation
Troubleshooting an MSTP Configuration
Displaying Debug Counters for Ports in an MST
Instance
The show spanning-tree debug-counters instance ports command allows you to
display the aggregate values of all MSTP debug counters maintained on one
or more ports used by a specified spanning-tree instance. These aggregate
values are a summary of information collected from the specified ports that
have VLANs assigned to the specified instance.
Use the show spanning-tree debug-counters instance ports command to
troubleshoot at a finer level the more general MSTP diagnostic information
displayed in show spanning-tree debug-counters instance command output
when you suspect unauthorized MSTP activity on one or more MST ports in
an MST instance.
The following examples shows sample output of the show spanning-tree debug-
counters instance ports command for both the CIST (default MST instance 0)
and an MST instance (instance 2) on port A15. For a description of each
counter, refer to Table 4-1 on page 4-66.
Syntax: show spanning-tree debug-counters instance <instance-id>
ports <port-list>
This command displays debug counters for MSTP activity on
the specified 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 an MST instance.
The ports <port-list> parameter specifies one or more MST ports
or trunk ports.
In the port list, enter a series of ports by separating the first
and last ports in the series with a dash (-); for example, a2-a8
or trk1-trk3. Separate individual ports and series of ports with
a comma; for example, a2-a8, a20, trk1, trk4-trk5.