First Hop Redundancy Protocols (FHRP)
Also known as: FHRP, first hop redundancy protocol
First Hop Redundancy Protocols (FHRPs) let multiple routers share a virtual IP and MAC address so hosts keep a working default gateway even if a router fails. The main FHRPs are HSRP, VRRP, and GLBP.
A First Hop Redundancy Protocol (FHRP) solves a single point of failure in LAN design: the default gateway. Hosts on a subnet are configured with one gateway IP address — their "first hop" out of the network — so if that router goes down, every host loses connectivity even when other routers exist on the same LAN. An FHRP lets two or more routers share a virtual IP address and virtual MAC address, presenting themselves to hosts as a single gateway.
Under the hood, one router is elected as the active (or master) forwarder for the virtual IP while the others stand by. The routers exchange periodic hello messages; if the active router stops responding, a standby router takes over the virtual IP and MAC within seconds. Hosts never change their configuration — they keep sending traffic to the same gateway address, unaware that a different physical router now handles it.
The three FHRPs to know are HSRP (Hot Standby Router Protocol, Cisco-proprietary, active/standby roles), VRRP (Virtual Router Redundancy Protocol, the open standard equivalent, master/backup roles), and GLBP (Gateway Load Balancing Protocol, Cisco-proprietary, which goes further by load-balancing traffic across multiple active forwarders instead of leaving standby routers idle).
The CCNA exam tests FHRPs in its IP connectivity domain. Know the purpose of a virtual IP and MAC address, the difference between the three protocols — especially which are Cisco-proprietary versus standards-based and which one load balances — and the failover behavior when the active router fails.
Key takeaways
- FHRPs eliminate the default gateway as a single point of failure by having multiple routers share a virtual IP and MAC address.
- One router actively forwards traffic while others stand by; hello messages detect failure and trigger automatic failover.
- HSRP is Cisco-proprietary (active/standby), VRRP is the open standard (master/backup), and GLBP adds load balancing across routers.
- Hosts keep the same gateway configuration through a failover — the switch is invisible to them.
- The CCNA tests FHRP purposes, protocol comparisons, and failover behavior in the IP connectivity domain.