if the primary root switch fails. This is assuming that the other network switches use the default switch priority of 32768, and therefore, are unlikely to become the root switch. You can execute this command on more than one switch to configure multiple backup root switches. Use the same network diameter and hello-time values that you used when you configured the primary root switch with the spanning-tree vlan vlan-id root primary global configuration command. To configure a secondary root device, perform this procedure: Procedure (Optional) Configuring Port Priority To configure port priority, perform this procedure:
Configuring Spanning Tree Protocol (Optional) Configuring Port Priority 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 spanning-tree vlan vlan-id root secondary [diameter net-diameter ] Example: Device(config)# spanning-tree vlan 20-24 root secondary diameter 4 Configures a device to become the secondary root for the specified VLAN. • For vlan-id, you can specify a single VLAN identified by VLAN ID number, a range of VLANs separated by a hyphen, or a series of VLANs separated by a comma. The range is 1 to 4094.
• (Optional) For diameter net-diameter, specify the maximum number of devices between any two end stations. The range is 2 to 7. Use the same network diameter value that you used when configuring the primary root switch. Step 4 end Example: Device(config)# end Returns to privileged EXEC mode. Configuring Spanning Tree Protocol 15