• Each interface can have only one backup interface.

• A backup interface can serve as a backup for only one other interface.

• Only one member of a primary and backup pair is active at any given time. An interface is automatically deactivated when configured as backup.

• The backup implementation does not protect against the failure of both interfaces. Therefore, if a backup interface fails while active, no switch to the primary interface is attempted.

When using frame relay encapsulation, the frame relay interface is considered down when its primary DLCI is down. The switchover back to the main interface occurs when the primary Data Link Connection Identifier (DLCI) is restored.