Explanation: Enabling PVST Spanning Tree
Spanning tree
is enabled on a per-VLAN basis. The switch maintains a separate instance of
spanning tree for each VLAN (except on VLANs on which you have disabled a
spanning tree). By default, spanning tree is enabled on all VLANs; therefore,
there is no need to take action to enable STP. If you have disabled spanning
tree and need to re-enable it for a particular VLAN, you can use the following
command from global configuration mode:
Switch(config)#spanning-tree vlan vlan_ID
This same command is used with additional arguments
to configure various features of STP.
– 
Verifying the Rapid PVST Configuration
A variety of
show commands can be used to display configuration and
operation information about spanning tree. The show
spanning-tree command takes several arguments to display a variety
of information about the STP configuration. Without any arguments, it will
display general information about all STP configurations.
The complete
syntax is as follows:
Switch#show spanning-tree [bridge-group |
active | backbonefast | {bridge [id]}| detail | inconsistentports |
{interface interface interface-number} | root | summary [total] |
uplinkfast | {vlanvlan-id} | {port-channelnumber} | pathcost-method]
Refer to your
software documentation for a complete explanation of each parameter.