Configuration Guide     318
Configuring Spanning Tree STP/RSTP Configurations
Switch#configure
Switch(config)#spanning-tree priority 36864
Switch(config)#spanning-tree timer forward-time 12
Switch(config)#show spanning-tree bridge
State      Mode     Priority     Hello-Time     Fwd-Time     Max-Age     Hold-Count     Max-Hops
-------     -----       --------      ------                 --------          --------           ---------              --------
Enable   Rstp       36864       2                         12                   20                  5                          20
Switch(config)#end
Switch#copy running-config startup-config
2.2.3  Enabling STP/RSTP Globally
Follow these steps to configure the spanning tree mode as STP/RSTP, and enable spanning 
tree function globally:
Step 1 configure
Enter global configuration mode.
Step 2 spanning-tree mode { stp | rstp }
Configure the spanning tree mode as STP/RSTP.
stp: Specify the spanning tree mode as STP .
rstp:
 
Specify the spanning tree mode as RSTP .
Step 3 spanning-tree
Enable spanning tree function globally.
Step 4 show spanning-tree active
(Optional) View the active information of STP/RSTP.
Step 5 end
Return to privileged EXEC mode. 
Step 6 copy running-config startup-config
Save the settings in the configuration file.
This example shows how to enable spanning tree function, configure the spanning tree 
mode as RSTP and verify the configurations:
Switch#configure
Switch(config)#spanning-tree mode rstp
Switch(config)#spanning-tree