Backup Root

When the root bridge of spanning tree instance is lost, its information may be retained in the network until the aging mechanism causes it to be removed. This leads to a delay in convergence on for the new root. This backup root feature is used to get faster convergence when the root bridge connectivity is lost.

Backup root feature enabled bridge port should be connected to Root with point to point link. When backup root bridge lost contact with the root bridge, automatically backup root bridge lowers its bridge priority (an increment below the priority of the lost root). This will cause the backup root bridge to become the new root with information superior to any information held by any bridge in the network. While save and reboot automatically changed priority will not be saved and restored. At the time of reboots it will have its priority restored to the original configured value by administrator.

If the priority of the root bridge is Zero and backup root has lost the connectivity of the root bridge then automatic assignment of the priority value for the backup root will be the initial configured value.

This backup root feature is activated only when there is loss of connectivity with the root bridge. Raising the priority on the root will not cause the Backup root feature to be activated.

Configuration Recommendations: