FHRP – First Hop Redundancy Protocol
(FHRP) is a hop redundancy protocol that is designed to provide redundancy to the gateway router within the organization’s network by the use of a virtual IP address and virtual MAC address.
To implement FHRP, there should be two or more routers that will be used as a gateway router. The virtual IP address and virtual MAC address will be used on both the router. The virtual IP address will be the default gateway IP address for all the devices inside the organization’s network. One router will be used as an active router (gateway router), and the other router will be standby. If the active router goes offline, the standby router will take its place to be the gateway router for all the hosts.
We have three ways to implement FHRP. These are by using the following First Hop Redundancy Protocols:
1-Hot Standby Router Protocol (HSRP)
HSRP, or Hot Standby Router Protocol, is a Cisco-proprietary router redundancy protocol that enables a cluster of routers to cooperate, and all routers are willing to be a default router. All the routers within the cluster will have the same virtual IP address and virtual mac address.
2-Virtual Router Redundancy Protocol (VRRP)
VRRP, Virtual Router Redundancy Protocol, is a vendor-neutral redundancy protocol that groups a cluster of physical routers (two or more routers) to produce a new single virtual router. It enables redundancy by assigning the same virtual gateway IP address and MAC address on all physical routers within the VRRP group. Currently, VRRP is at version 2. It almost has the same concept as HSRP. The only difference is that preemption is enabled by default on VRRP, while on HSRP, it needs to be configured manually.
3-Gateway Load Balancing Protocol (GLBP)
As compared to HSRP and VRRP, Gateway Load Balancing Protocol is a bit different. With GLBP, routers within the group are allowed to do load balancing. To put it simply, all the traffic that is transmitted to the default gateway IP address will be load-balanced one at a time or in a round-robin manner among the routers within the group. GLBP has the same state as HSRP, which is called active and standby. The mechanism of GLBP’s active and standby state is the same as HSRP’s active and standby state.
