H3C s5820x series, High Availability Configuration Manual, Page: 128 / 233

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Configuring a default route for network hosts facilitates your configuration, but also requires high
performance stability of the device that acts as the gateway. Using more egress gateways is a common
way to improve system reliability, but introduces the problem of routing among the egresses.
Virtual Router Redundancy Protocol (VRRP) is designed to address this problem. VRRP adds a group of
routers that can act as network gateways to a VRRP group, which forms a virtual router. Using the VRRP
election mechanism, routers in the VRRP group elect a master to act as a gateway. Hosts on a LAN only
need to configure the virtual router as their default network gateway.
VRRP is an error-tolerant protocol. It improves network reliability and simplifies configurations on hosts.
On a multicast and broadcast LAN such as Ethernet, VRRP provides highly reliable default links without
configuration changes—such as dynamic routing protocols, route discovery protocols—when a router
fails, and prevents network interruption due to a single link failure.
VRRP works in either of the following modes:
•
Standard protocol mode—Includes two versions VRRPv2 and VRRPv3 based on RFCs. VRRPv2 is
based on IPv4, and VRRPv3 is based on IPv6. The two versions implement the same functions but
are applied in different network environments. For more information, see “ VRRP standard protocol
mode .”
•
Load balancing mode—Extends the standard protocol mode and realizes load balancing. For
more information, see “
VRRP load balancing mode .”
VRRP standard protocol mode
Introduction to VRRP group
VRRP combines a group of routers—including a master and multiple backups—on a LAN into a virtual
router called a VRRP group.
A VRRP group has the following features:
• A virtual router has a virtual IP address. A host on the LAN only needs to know the IP address of the
virtual router to use the IP address as the next hop of the default route.
•
Every host on the LAN communicates with external networks through the virtual router.
• Routers in the VRRP group elect a master that acts as the gateway according to their priorities. The
other routers function as backups. When the master fails, to ensure that the hosts in the network
segment can uninterruptedly communicate with the external networks, the backups in the VRRP
group elect a new master to act as the gateway.