What is FHRP and its role in WAN networks?

FHRP (First Hop Redundancy Protocol)  promotes transparent failover at the first-hop IP router.

enable two or more devices to work together in a group, sharing a single IP address, the virtual IP address. The virtual IP address is configured in each end user's workstation as a default gateway address and is cached in the host's Address Resolution Protocol (ARP) cache. In an HSRP group, one router is elected to handle all requests sent to the virtual IP address. With HSRP, this is the active router. An HSRP group has one active router, at least one standby router, and perhaps many listening routers.

FHRP is First hop redundancy protocol and this is used to have a redundancy in network(There will be a Master and backup router in FHRP to reach WAN or network and In case any router went down the other router will continue forwarding the packets which were destined to Master router)

There are number of protocols which will be used in FHRP as HSRP,VRRP,GLBP,RSMLT and many based on Vendors there are vendor specific protocols as well.

First Hop Redundancy Protocol (FHRP) is a group of protocols that allow a router on a LAN network to automatically take over if primary default gateway router

IP routing redundancy is designed to allow for transparent fail-over at the first-hop IP router.

1- Virtual IP addressing. I prefer Ghost IP.

2- Redundancy and seamless failover at first hop.

3- Loving it.

HSRP enable two or more devices to work together in a group, sharing a single IP address, the virtual IP address. The virtual IP address is configured in each end user's workstation as a default gateway address and is cached in the host's Address Resolution Protocol (ARP) cache.