Cisco ME 3600X, Command Reference Manual

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Cisco ME 3800X and ME 3600X Switch Command Reference
OL-28238-01
Chapter
spanning-tree mst root
spanning-tree mst root
Use the spanning-tree mst root global configuration command to configure the multiple spanning-tree
(MST) root switch priority and timers based on the network diameter. Use the no form of this command
to return to the default settings.
spanning-tree mst instance-id root { primary | secondary } [ diameter net-diameter
[ hello-time seconds ]]
no spanning-tree mst instance-id root
Syntax Description
Defaults
The primary root switch priority is 24576.
The secondary root switch priority is 28672.
The hello time is 2 seconds.
Command Modes
Global configuration
Command History
Usage Guidelines Use the spanning-tree mst instance-id root command only on backbone switches.
When you enter the spanning-tree mst instance-id root command, the software tries to set a high
enough priority to make this switch the root of the spanning-tree instance. Because of the extended
system ID support, the switch sets the switch priority for the instance to 24576 if this value will cause
this switch to become the root for the specified instance. If any root switch for the specified instance has
a switch priority lower than 24576, the switch sets its own priority to 4096 less than the lowest switch
priority. (4096 is the value of the least-significant bit of a 4-bit switch priority value.)
instance-id Range of spanning-tree instances. You can specify a single instance, a range
of instances separated by a hyphen, or a series of instances separated by a
comma. The range is 0 to 4094.
root primary Forces this switch to be the root switch.
root secondary Sets this switch to be the root switch should the primary root switch fail.
diameter net-diameter (Optional) Sets the maximum number of switches between any two end
stations. The range is 2 to 7. This keyword is available only for MST
instance 0.
hello-time seconds (Optional) Sets the interval between hello bridge protocol data units
(BPDUs) sent by the root switch configuration messages. The range is 1 to 10
seconds. This keyword is available only for MST instance 0.
Release Modification
12.2(52)EY This command was introduced.