First-hop redundancy protocols
Why hosts need a redundant default gateway and how HSRP, VRRP and GLBP provide virtual gateway failover at concept level.
Hosts know exactly one default gateway. If that router dies, the subnet is cut off even when a second path exists — FHRPs solve this by presenting a virtual gateway: a virtual IP (and virtual MAC) shared by two or more routers. The host's gateway never changes; the active role moves between routers.
FHRP protocols compared
| Protocol | Vendor | Roles | Load balancing | Virtual MAC |
|---|---|---|---|---|
| HSRP | Cisco | Active + Standby (+ listeners) | One active per group — balance via multiple groups | 0000.0c07.acXX (XX = group) |
| VRRP | Open (RFC 5798) | Master + Backup(s) | One master per group | 0000.5e00.01XX |
| GLBP | Cisco | AVG + AVFs | Per-client round-robin virtual MACs — true balancing in one group | 0007.b400.XXYY |
FHRP defaults (HSRP)
| Parameter | Default |
|---|---|
| Hello timer | 3 s |
| Hold timer | 10 s |
| Priority | 100 (higher wins) |
| Preemption | Disabled by default |
| Virtual MAC (HSRPv1) | 0000.0c07.acXX — v2 uses 0000.0c9f.fXXX; the MAC alone does not identify the physical active router |
With HSRP preemption off, a recovered higher-priority router does NOT take back the active role (VRRP would preempt).
Preemption controls whether a router with higher priority takes the active/master role back after recovering. In HSRP it is off by default — like OSPF DR election, the incumbent keeps the role — while VRRP preempts by default. Enable standby <g> preempt on HSRP where deterministic roles matter. Tracking (standby <g> track <interface>) decrements priority when an uplink fails so the standby with a live upstream path wins.
Related resources
Sources
- Cisco CCNA 200-301 v1.1 Exam Topics (official PDF) — reviewed 2026-11-02
- RFC 5798 — Virtual Router Redundancy Protocol (VRRP) Version 3 — reviewed 2026-11-02
Targets CCNA 200-301 v1.1 objectives. Supplemental blocks are labeled beyond exam scope.