Configuration Guide     216
Configuring Spanning Tree STP/RSTP Configurations
Note:
To prevent frequent network flapping, make sure that Hello Time, Forward Delay, and Max Age 
conform to the following formulas:
• 
2*(Hello Time + 1) <= Max Age
• 
2*(Forward Delay - 1) >= Max Age
This example shows how to configure the priority of the switch as 36864, the Forward 
Delay as 12 seconds:
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.