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

Related Topics
Root Switch, on page 244
Specifying the MST Region Configuration and Enabling MSTP , on page 261
Restrictions for MSTP, on page 242
Bridge ID, Device Priority, and Extended System ID, on page 214
Configuring a Secondary Root Switch , on page 265

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.
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. enable
2. configure terminal
3. spanning-tree mst instance-id root secondary
4. end
DETAILED STEPS
Command or Action
Step 1
enable
Example:
Switch> enable
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
Purpose
Enables privileged EXEC mode. Enter your password if
prompted.
How to Configure MSTP Features
265