Spanning-Tree Operation

802.1s Multiple Spanning Tree Protocol (MSTP)

Enabling or Disabling Spanning Tree Operation

This command enables or disables spanning tree operation for any spanning tree protocol enabled on the switch. Before using this command to enable spanning tree, ensure that the version you want to use is active on the switch.

Syntax: [no] spanning-tree

Enabling spanning tree with MSTP configured implements MSTP for all physical ports on the switch, according to the VLAN groupings for the IST instance and any other configured instances. Disabling MSTP removes protection against redundant loops that can significantly slow or halt a network. This command simply turns spanning tree on or off. It does not change the existing spanning tree configuration.

Enabling an Entire MST Region at Once or Exchanging One Region Configuration for Another

Command

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spanning-tree pending < apply config-name config-revision instance reset >

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This operation exchanges the currently active MSTP configuration with the currently pending MSTP configuration. It enables you to implement a new MSTP configuration with minimal network disruption or to exchange MSTP configurations for testing or troubleshooting purposes.

When you configure or reconfigure MSTP, the switch re-calculates the corre­ sponding network paths. This can have a ripple effect throughout your net­ work as adjacent MSTP switches recalculate network paths to support the configuration changes invoked in a single switch. Although MSTP employs RSTP operation, the convergence time for implementing MSTP changes can be disruptive to your network. However, by using the spanning-tree pending feature, you can set up an MSTP on the switch and then invoke all instances of the new configuration at the same time, instead of one at a time.

To Create a Pending MSTP Configuration. This procedure creates a pending MSTP configuration and exchanges it with the active MSTP configu­ ration.

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