Configuring A Secondary Root Switch - Cisco Catalyst 2960-XR Configuration Manual

Configuring Multiple Spanning-Tree Protocol
Configuring a Secondary Root Switch, on page 63

Configuring a Secondary Root Switch

When you configure a switch with the extended system ID support as the secondary root, the switch priority
is modified from the default value (32768) to 28672. The switch is then likely to become the root switch for
the specified instance if the primary root switch fails. This is assuming that the other network switches use
the default switch priority of 32768 and therefore are unlikely to become the root switch.
You can execute this command on more than one switch to configure multiple backup root switches. Use the
same network diameter and hello-time values that you used when you configured the primary root switch
with the spanning-tree mst instance-id root primary global configuration command.
This procedure is optional.
Beginning in privileged EXEC mode, follow these steps to configure a secondary root switch.
Before You Begin
A multiple spanning tree (MST) must be specified and enabled on the switch. For instructions, see Related
Topics.
You must also know the specified MST instance ID. This example uses 0 as the instance ID because that was
the instance ID set up by the instructions listed under Related Topics.
SUMMARY STEPS
1. configure terminal
2. spanning-tree mst instance-id root secondary
3. end
DETAILED STEPS
Command or Action
Step 1
configure terminal
Example:
Switch# configure terminal
Step 2 spanning-tree mst instance-id root secondary
Example:
Switch(config)# spanning-tree mst 0 root
secondary
Step 3
end
Example:
Switch(config)# end
OL-29424-01
Purpose
Enters the global configuration mode.
Configures a switch as the secondary root switch.
For instance-id, 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.
Returns to privileged EXEC mode.
Catalyst 2960-XR Switch Layer 2 Configuration Guide, Cisco IOS Release 15.0(2)EX1

Configuring a Secondary Root Switch

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