Multiple Instance Spanning-Tree Operation

Configuring 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.

 

 

N o t e

The convergence time for implementing MSTP changes can be disruptive to

 

your network. To minimize such disruption, consider using the spanning-tree

 

pending command (refer to the following section on “Enabling an Entire MST

 

Region at Once or Exchanging One Region Configuration for Another”).

 

Enabling an Entire MST Region at Once or

 

 

Exchanging One Region Configuration for Another

 

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

 

rapid spanning-tree 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.

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