Is preemption enabled on First Hop Redundancy Protocols (FHRPs) by default?

In the context of First Hop Redundancy Protocols (FHRPs) like HSRP (Hot Standby Router Protocol), VRRP (Virtual Router Redundancy Protocol), and GLBP (Gateway Load Balancing Protocol), preemption is not enabled by default. Preemption is the ability of a higher-priority router to take over the active role from a lower-priority one once it becomes available again.

For most FHRPs, including HSRP and VRRP, preemption must be explicitly configured by the network administrator. This is important for ensuring predictable failover behavior and maintaining the desired router hierarchy within a network. In environments where automatic failover might lead to instability – such as in networks where link flaps are common – having preemption disabled by default helps prevent unnecessary disruption caused by frequent state changes.

Furthermore, while GLBP allows for load balancing among multiple routers and can also include preemption, it still does not have preemption enabled by default. Understanding that preemption requires specific configuration helps ensure that network administrators are aware of the behavior of the network redundancy protocols they are using, allowing for better control of network performance and reliability.

Thus, the assumption that preemption is enabled by default for FHRPs is