What is the purpose of Priority Delta in VRRP?

The effective priority in the context of Virtual Router Redundancy Protocol (VRRP) is a crucial concept that determines which router will take over as the master when the current master becomes unavailable. Priority Delta plays an important role in this dynamic.

When a router interface fails, the effective priority is adjusted by subtracting the Priority Delta from the configured Priority. This adjustment serves to lower the priority of the failing router, making it less favorable to assume the master role if it recovers. It helps ensure that the backup router, which maintains a higher effective priority, becomes the new master, providing a more robust failover mechanism. This behavior enhances network reliability by preventing a router that has just failed from quickly regaining the master role upon recovery, especially if it was once the master.

The other choices present scenarios that do not align with how Priority Delta functions in the context of router failures. For instance, effective priority being adjusted positively (either by adding the Delta or during an interface failure) does not accurately reflect the design and intention of VRRP. Thus, understanding this mechanism is integral to managing redundancy and failover responsiveness in VRRP setups effectively.