VRRP (Virtual Router Redundancy Protocol)

Definition

VRRP (Virtual Router Redundancy Protocol, RFC 5798) is a networking protocol that provides automatic assignment of available routers to participating hosts. It increases router availability and reliability by allowing multiple routers to act as a single virtual router.

VRRP is the foundation of high-availability gateway configurations — if the primary router fails, a backup router seamlessly takes over the virtual IP address.

How VRRP Works

Virtual IP: 192.168.1.254 (shared by all VRRP routers)

Router A (Master, priority 200) → Handles traffic for 192.168.1.254
Router B (Backup, priority 100) → Standby, monitors Router A
Router C (Backup, priority 150) → Second standby

If Router A fails:
  Router C (highest priority among backups) → Takes over 192.168.1.254
  Clients continue using 192.168.1.254 without reconfiguration

Key Concepts

• Virtual Router: The logical router (IP + MAC) that clients use as their default gateway
• Master Router: The router currently handling traffic for the virtual router
• Backup Routers: Routers ready to take over if the master fails
• Priority: 1-254 (higher = more likely to be master); 255 = IP address owner
• Preemption: Higher priority backup can take over from lower priority master
• Advert Interval: How often master sends VRRP advertisements (default 1s)
• VRRP Version: VRRPv2 (IPv4, RFC 3768), VRRPv3 (IPv4/IPv6, RFC 5798)

VRRP vs HSRP vs GLBP

VRRP Configuration Example (Linux/iproute2)

# On Master router
vrrpd -f /etc/vrrpd.conf
# /etc/vrrpd.conf:
# vrrp_instance VI_1 {
#     state MASTER
#     interface eth0
#     virtual_router_id 51
#     priority 200
#     advert_int 1
#     authentication {
#         auth_type pass
#         auth_pass secret
#     }
#     virtual_ipaddress {
#         192.168.1.254
#     }
# }

# On Backup router (same config, state BACKUP, priority 100)

VRRP in Infrastructure

Related Terms

• Keepalived — Linux implementation of VRRP
• Ha — VRRP for redundant firewall pairs
• Load Balancer