Cisco 7604 User Manual

19-20
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 19 Configuring Standard-Compliant IEEE MST
Configuring MST
To configure a router as the root bridge, perform this task:
To return the router to its default setting, use the no spanning-tree mst instance_id root global
configuration command.
Configuring a Secondary Root Bridge
When you configure a router with the extended system ID support as the secondary root, the switch
priority is modified from the default value (32768) to 28672. The router is then likely to become the root
bridge for the specified instance if the primary root bridge fails. This is assuming that the other network
routers use the default switch priority of 32768 and therefore are unlikely to become the root bridge.
You can execute this command on more than one router to configure multiple backup root bridges. Use
the same network diameter and hello-time values that you used when you configured the primary root
bridge with the spanning-tree mst instance_id root primary global configuration command.
Command Purpose
Step 1
Router(config)# configure terminal
Enters global configuration mode.
Step 2
Router(config-config)# spanning-tree mst
instance_id root primary [diameter net_diameter
[hello-time seconds ]]
(Optional) Configures a router as the root bridge.
• 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.
• (Optional) For diameter net_diameter, specify the
maximum number of Layer 2 hops between any two
end stations. The range is 2 to 7. This keyword is
available only for MST instance 0.
• (Optional) For hello-time seconds, specify the
interval in seconds between the generation of
configuration messages by the root bridge. The range
is 1 to 10 seconds; the default is 2 seconds.
Step 3
Router(config-config)# end
Returns to privileged EXEC mode.
Step 4
Router# show spanning-tree mst instance_id
Verifies your entries.
Step 5
Router# copy running-config startup-config
(Optional) Saves your entries in the configuration file.

Cisco 7604 Specifications

General

Brand	Cisco
Model	7604
Category	Network Router
Language	English