First-Hop Redundancy Protocols Explained
First-Hop Redundancy Protocols (FHRPs) solve a single point of failure: every device's traffic leaves through its default gateway — if that one router dies, everyone loses connectivity even though the rest of the network is fine. FHRPs make two or more routers share one virtual gateway that survives any single failure.
The shared virtual gateway idea
Hosts are configured with a virtual IP as their gateway — an address owned by the FHRP group, not any physical router. One router actively answers for it; others stand by, monitoring via hellos. When the active fails, a standby takes over the virtual IP (and its virtual MAC) within seconds — hosts never notice or change configuration.
The three protocols
Common mistakes
Forgetting preemption (in HSRP it's off by default — a recovered high-priority router won't reclaim Active), mismatched group numbers or virtual IPs between routers, and testing only the happy path. Always verify failover by actually failing the active router — see the HSRP lab.
Frequently asked questions
What problem do FHRPs solve?
The default gateway as a single point of failure — FHRPs let multiple routers share one virtual gateway address so a router failure doesn't strand every host.
What is the difference between HSRP, VRRP and GLBP?
HSRP (Cisco) and VRRP (open standard) run active/standby with one forwarder; GLBP (Cisco) load-balances actively across multiple routers simultaneously.
What is the virtual IP in an FHRP?
A gateway address owned by the redundancy group rather than any single router — hosts use it as their gateway, and whichever router is active answers for it.
Do hosts notice an FHRP failover?
Ideally no — the standby takes over the same virtual IP and MAC within seconds, so host configuration and connections continue unchanged.
Related articles
Want hands-on training?
Learn this on real Cisco lab devices with placement support at Attila Technologies, Ahmedabad.