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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 9 Configuring STP
Configuring Basic STP Features
Configuring a Secondary Root Switch
When you configure a switch as the secondary root, the STP switch priority is changed from the default
value (32768) to 16384 so that the switch is likely to become the root switch for the specified VLAN if
the primary root switch fails (if the other switches in the network 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 as you used when configuring the primary root switch.
Beginning in privileged EXEC mode, follow these steps to configure a switch as the secondary root
switch:
To return the switch to its default setting, use the no spanning-tree vlan vlan-id root global
configuration command.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
spanning-tree vlan vlan-id root secondary
[diameter net-diameter [hello-time
seconds]]
Configure a switch as the secondary root switch.
For vlan-id, the range is 1 to 1005. Do not enter leading zeroes.
(Optional) For diameter net-diameter, specify the maximum number
of switches between any two end stations. The range is 2 to 7.
(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 for STP.
Use the same network diameter and hello-time values that you used
when configuring the primary root switch.
Step 3
end Return to privileged EXEC mode.
Step 4
show spanning-tree Verify your entries.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.
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