VRRP / HSRP

networking

Stands for: Virtual Router Redundancy Protocol (and the first-hop redundancy family: HSRP, GLBP)

The first-hop redundancy family - VRRP (the open standard) and Cisco's HSRP: two or more routers share one virtual gateway IP and MAC, so the default gateway survives a device failure.

The trick is that hosts never learn a real router's address: they point at a virtual IP owned by whichever router currently holds the master role (VRRP, RFC 5798, virtual MAC 0000.5e00.01xx) or active role (HSRP, the Cisco precursor that shaped the idea). Election runs on priority; preemption decides whether a recovered ex-master takes the job back; a gratuitous ARP announces the changeover so switches relearn the port. Cisco's GLBP variant adds load-balancing across gateways instead of an idle standby. The family name is FHRP - first-hop redundancy protocol - and the design question is always the same: milliseconds of failover for the one address every host depends on.

Also known as: vrrp, hsrp, glbp, fhrp, first hop redundancy, virtual gateway

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