Specifications

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Catalyst 4500 Series Switch Cisco IOS Command Reference—Release IOS XE 3.3.0XO(15.1(1)XO)

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Chapter 2 Cisco IOS Commands for the Catalyst 4500 Series Switches

spanning-tree mst root

To designate the primary root, secondary root, bridge priority, and timer value for an instance, use the

spanning-tree mst root command. To return to the default settings, use the no form of this command.

spanning-tree mst instance-id root {prima ry | secondary} | {priority prio} [diameter dia

[hello-time hello]]

no spanning-tree mst root

Syntax Description

Defaults Br idge priority is 32768.

Command Modes Global c onfiguratio n mode

Usage Guidelines T he bridge priority can be se t in increments of 4096 only. When you set the priority, valid values are 0,

4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768 , 36864, 40960, 45056, 49 152, 53248, 57344,

and 61440.

You can set the priority to 0 to make the switch root.

The spanning-tree root secondary bridge priority value is 16384.

The diameter dia and hello-time hello options are available for instance 0 only.

If you do not specify the hello_time value, the value is calculated from the network diameter.

Examples This example shows how to set the priority and timer values for the bridge:

Switch(config)# spanning-tree mst 0 root primary diameter 7 hello-time 2

Switch(config)# spanning-tree mst 5 root primary

Related Commands

instance-id Instance identification number; valid values are from 1 to 15.

root Configures switch as the root switch.

primary S ets a high enough priority (low value) to make the bridge root of the spanning-tree

instance.

secondary Designates this switch as a secondary root if the primary root fails.

priority prio Sets the bridge priority; see the “Usage Guidelines” section for valid values and

additional information.

diameter dia (Optional) Sets the timer values for the bridge based on the network diameter; valid

values are from 2 to 7.

hello-time hello (Optional) Specifies the duration between the generation of configuration messages

by the root sw itch.

Command Description

show spanning-tree mst Displays MST proto col information.