Multiple Instance Spanning-Tree Operation

Troubleshooting an MSTP Configuration

Troubleshooting an MSTP Configuration

Command

Page

show spanning-tree root-history

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show spanning-tree debug counters

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

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

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ports <port-list>

 

 

 

This section describes the show spanning-treecommands that you can use to monitor, troubleshoot, and debug the operation of a multiple-instance spanning -tree configuration in your network.

Note that the show spanning-treecommands described in this section allow you to troubleshoot MSTP activity in your network by focusing on increasingly specific levels of operation. For example, you can display debug information for:

All MST instances

All ports used in one MST instance

A specific port or several ports used in one MST instance

Also, you can display the change history for the root (bridge) switch used as the single forwarding path for:

All MST regions, STP bridges, and RSTP bridges in an STP network

All VLANs on MSTP switches in a region

All VLANs on MSTP switches in an MST instance

Displaying the Change History of Root Bridges

The show spanning-treeroot-historycommand allows you to display change history information (up to 10 history entries) for a specified root bridge in any of the following MSTP topologies:

Common Spanning Tree (cst): Provides connectivity in a bridged network between MST regions, STP LANs, and RSTP LANs.

Internal Spanning Tree (ist): Provides connectivity within an MST region for VLANs associated with the default Common and Internal Spanning Tree (CIST) instance in your network (VLANs that have not been mapped to an MST instance).

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