(Optional) Disabling Spanning Tree Spanning tree is enabled by default on VLAN 1 and on all newly created VLANs up to the spanning-tree limit. Disable spanning tree only if you are sure that there are no loops in the network topology. When spanning tree is disabled and loops are present in the topology, excessive traffic and indefinite packet duplication can drastically reduce network performance. Caution To disable spanning tree, perform this procedure:
Procedure (Optional) Configuring the Root Device To configure a device as the root for the specified VLAN, use the spanning-tree vlan vlan-id root global configuration command to modify the device priority from the default value (32768) to a significantly lower value. When you enter this command, the software checks the switch priority of the root switches for each VLAN. Because of the extended system ID support, the switch sets its own priority for the specified VLAN to 24576 if this value causes this switch to become the root for the specified VLAN.
Configuring Spanning Tree Protocol (Optional) Disabling Spanning Tree Command or Action Purpose Device# clear spanning-tree detected-protocols restarts the protocol migration process on the entire device. This step is optional if the designated device detects that this device is running rapid PVST+. Command or Action Purpose Step 1 enable Example: Device> enable Enables privileged EXEC mode. Enter your password if prompted. Step 2 configure terminal Example: Device# configure terminal Enters global configuration mode. Step 3 no spanning-tree vlan vlan-id Example: Device(config)# no spanning-tree vlan 300 For vlan-id, the range is 1 to 4094. Step 4 end Example:
Device(config)# end Returns to privileged EXEC mode. Configuring Spanning Tree Protocol 13