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Catalyst 2960 Switch SoftwareConfiguration Guide
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Chapter16 Configuring MSTP
Configuring MSTP Features
forward-delay time, and maximum-age time for a network of that diameter, which can significantly
reduce the convergence time. You can use the hello keyword to override the automatically calculated
hello time.
Note After configuring the switch as the root switch, we recommend that you avoid manually configuring the
hello time, forward-delay time, and maximum-age time t hrough the spanning-tree mst hello-time,
spanning-tree mst forward-time, and the spanning-tree mst max-age global configuration
commands.
Beginning in privileged EXEC mode, follow these steps to configure a switch as the root switch. This
procedure is optional.
To return the switch to its default setting, use the no spanning-tree mst instance-id root global
configuration command.
Configuring a Secondary Root Switch
When you configure a switch with the extended system ID support as t he secondary root, the switch
priority is modified from the default value (32768) to 28672. The switch is then li kely 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 th e 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 w hen you configured the primary root
switch with the spanning-tree mst instance-id root primary global configuration command.
Beginning in privileged EXEC mode, follow these steps to configure a switch as the secondary root
switch. This procedure is optional.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 spanning-tree mst instance-id root primary
[diameter net-diameter [hello-time seconds]]
Configure a switch as the 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 15.
•(Optional) For diameter net-diameter, specify the
maximum number of switches between any two end
stations. The range is2 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 switch. The range is 1 to 10 seconds; the
default is 2 seconds.
Step3 end Return to privileged EXEC mode.
Step4 show spanning-tree mst instance-id Verify your entries.
Step5 copy running-config startup-config (Optional) Save your entries in the configuration file.