Spanning-Tree Mst Root - Cisco Catalyst 2950 Command Reference Manual
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Also See for Catalyst 2950:
- Configuration manual (710 pages) ,
- Command reference manual (686 pages) ,
- Software configuration manual (674 pages)
Table of Contents
Chapter 2 Cisco IOS Commands
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 setting.
This command is available only if your switch is running the enhanced software image (EI).
Syntax Description
instance-id
root primary
root secondary
diameter net-diameter
hello-time seconds
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
Release
12.1(9)EA1
Usage Guidelines
Use the spanning-tree mst instance-id root command used 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.)
When you enter the spanning-tree mst instance-id root secondary command, because of support for
the extended system ID, the software changes the switch priority from the default value (32768) to
28672. If the root switch fails, this switch becomes the next root switch (if the other switches in the
network use the default switch priority of 32768 and are therefore unlikely to become the root switch).
78-11381-05
spanning-tree mst instance-id root {primary | secondary} [diameter net-diameter
[hello-time seconds]]
no spanning-tree mst instance-id root
ID associated with a MST instance. The range is 0 to 15.
Force this switch to be the root switch.
Set this switch to be the root switch should the primary root switch fail.
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.
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.
Modification
This command was first introduced.
Catalyst 2950 Desktop Switch Command Reference
spanning-tree mst root
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