Simple definition
First-hop redundancy protocols provide a shared virtual default gateway across routers to preserve connectivity during a failure.
Purpose and use
A FHRP, First Hop Redundancy Protocol, maintains a virtual default gateway when a local router becomes unavailable.
How does it work?
Routers share a virtual identity and coordinate an active role or forwarding distribution, depending on protocols such as VRRP, HSRP or GLBP.
Example and verification
A useful test interrupts the path actually being monitored, then checks client recovery and access to a remote destination.
Points to watch
A router may remain active on the LAN after losing its WAN connection. Interface or connectivity tracking therefore affects failover behavior.
In short
First-hop redundancy protects the local gateway; it does not by itself guarantee availability of a remote service.