Spanning-Tree Mst Root - Cisco 4500M Command Reference Manual

Chapter2 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 the command.
Syntax Description
instance-id
root
primary
secondary
priority prio
diameter dia
hello-time hello
Defaults
Bridge priority is 32768.
Command Modes
Global configuration
Command History Release
12.1(12c)EW
Usage Guidelines
The bridge priority can be set 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, 49152, 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 bridge priority:
Switch(config)# spanning-tree mst 0 root priority 4096
Switch(config)#
78-16201-01
spanning-tree mst instance-id root {primary | secondary} | {priority prio} [diameter dia
[hello-time hello]]
no spanning-tree mst root
Instance identification number; valid values are from 1 to 15.
Configures switch as the root switch.
Sets a high enough priority (low value) to make the bridge root of the spanning-tree
instance.
Designates this switch as a secondary root, if the primary root fails.
Sets the bridge priority; see the "Usage Guidelines" section for valid values and
additional information.
(Optional) Sets the timer values for the bridge based on the network diameter; valid
values are from 2 to 7.
(Optional) Specifies the duration between the generation of configuration messages
by the root switch.
Modification
Support for this command was introduced on the Catalyst 4500 series switch.
Catalyst4500 Series SwitchCiscoIOS Command Reference—Release 12.2(18)EW
spanning-tree mst root
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