Overview of VRRP

Definition

The Virtual Router Redundancy Protocol (VRRP) specifies an election protocol that dynamically assigns responsibility for a virtual router to VRRP routers on a LAN. It allows several routers on a subnet to use the same virtual IP address, with the physical routers representing a virtual logical router. There are two roles in VRRP: master and backup. The master represents the virtual router and forwards traffic. If the master fails, the backup router can automatically take the responsibilities for forwarding traffic.

Purpose

As networks rapidly develop and applications become more diverse, various value-added services (VASs) such as Internet Protocol television (IPTV) and video conferencing have become increasingly widespread. Users require a reliable network infrastructure to ensure uninterrupted transmission.

Generally, all hosts on one network segment are configured with the same default route, which has the gateway address as the next hop address. The hosts use the default route to send packets to the gateway, which forwards the packets to other network segments. When the gateway fails, all hosts on this network segment are cut off from the rest of the network. To improve network reliability, multiple egress gateways can be configured. However, route selection between the gateways becomes an issue.

VRRP resolves this issue by virtualizing a group of routers into a single virtual router without changing the networking. The virtual router IP address is configured as the default gateway address. When a gateway fails, VRRP selects a new gateway to transmit service traffic, ensuring reliable communication.

Benefits

With VRRP, you can configure multiple routers as the default gateway router. If a single point of failure occurs on the network, a backup link is used to transmit traffic, ensuring uninterrupted transmission.

VRRP enables multiple available routers to share the load more uniformly, reducing the traffic burden on the master.

• VRRP can detect faults on the uplink. When the upstream interface or uplink is faulty, the priority of the original master decreases, and an optimal backup becomes the master, ensuring proper traffic forwarding.
• VRRP can associate with BFD to speed up the master/backup switchover in the VRRP group. BFD can fast detect faults. Therefore, you can configure a BFD session between the master and backup and associate the BFD session with the VRRP group. When the link between the master and backup becomes Down, the backup immediately becomes the master and takes over traffic.