Enabling the Backup Root Function

Disabled by default, the backup root function works only when the backup root-enabled bridge is directly connected to the root bridge. The backup root function prevents stale Spanning Tree information from circulating throughout the network in the event that the link between the root bridge and the backup root-enabled bridge is lost. If this happens, the backup root will dynamically lower its bridge priority relative to the existing root bridge's priority, causing it to immediately be selected as the new root bridge.

Use this command to enable the backup root function on an SID:

set spantree backuproot sid enable

When SNMP trap messaging is configured and the backup root function is enabled, a trap message will be generated when the backup becomes the new root of the network.