Specifications

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Cisco ME 3400 Ethernet Access Switch Command Reference
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Chapter 2 Cisco ME 3400 Ethernet Access Switch Cisco IOS Commands
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 Spanning Tree Protocol (STP) is not supported on user network interfaces (UNIs); it is only supported
on network node interfaces (NNIs) or on enhanced network interfaces (ENIs) on which STP has been
enabled. To set a port as an ENI or NNI, enter the port-type {eni | nni} interface configuration
command. To enable STP on an ENI, enter the spanning-tree interface configuration command.
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
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 Force this switch to be the root switch.
root secondary Set this switch to be the root switch should the primary root switch fail.
diameter net-diameter (Optional) Set 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) Set 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(25)EX This command was introduced.
12.2(25)SEG The instance-id range changed to 0 to 4094.