Cisco 4500M Command Reference Manual page 482

spanning-tree vlan
Usage Guidelines
When you are setting the max-age seconds value , if a bridge does not hear BPDUs from the root bridge
within the specified interval, it assumes that the network has changed and recomputes the spanning tree
topology.
The spanning-tree root primary command alters the switch bridge priority to 8192. If you enter the
spanning-tree root primary command and the switch does not become root, then the bridge priority is
changed to 100 less than the bridge priority of the current bridge. If the switch does not become root, an
error will result.
The spanning-tree root secondary command alters the switch bridge priority to 16384. If the root
switch fails, this switch becomes the next root switch.
Use the spanning-tree root commands on backbone switches only.
Examples
This example shows how to enable spanning tree on VLAN 200:
Switch(config)# spanning-tree vlan 200
Switch(config)#
This example shows how to configure the switch as the root switch for VLAN 10 with a network
diameter of 4:
Switch(config)# spanning-tree vlan 10 root primary diameter 4
Switch(config)#
This example shows how to configure the switch as the secondary root switch for VLAN 10 with a
network diameter of 4:
Switch(config)# spanning-tree vlan 10 root secondary diameter 4
Switch(config)#
Related Commands
spanning-tree cost
spanning-tree port-priority
spanning-tree portfast default
spanning-tree portfast (interface configuration mode)
spanning-tree uplinkfast
show spanning-tree
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