H3C Technologies H3C MSR 5600 - Manual (Page 9)

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Configuring VRRP
Overview
Typically, you can configure a default gateway for every host on a LAN. All packets destined for other
networks are sent through the default gateway. As shown in Figure 1 , when the default gateway fails, no
hosts can communicate with external networks.
Figure 1 LAN networking
Using a default gateway facilitates your configuration but requires high availability. Using more egress
gateways improves link availability but introduces the problem of routing among the egresses.
Virtual Router Redundancy Protocol (VRRP) is designed to address this issue. VRRP adds a group of
network gateways to a VRRP group called a "virtual router." A VRRP group comprises one master and
multiple backups, but has only one virtual IP address. The hosts on the subnet only need to configure this
virtual IP address as their default network gateway for communicating with external networks.
The virtual IP address of the virtual router can be either an unused IP address on the subnet where the
VRRP group resides or the IP address of an interface on a router in the VRRP group. In the latter case, the
router is called the IP address owner. A VRRP group can have only one IP address owner.
VRRP avoids single points of failure and simplifies the configuration on hosts. When the master in the
VRRP group on a multicast or broadcast LAN (for example, an Ethernet network) fails, another router in
the VRRP group can take over as the master without causing dynamic route recalculation, route
re-discovery, gateway reconfiguration on the hosts, or traffic interruption.
VRRP operates in either of the following modes:
• Standard mode—Implemented based on RFCs. For more information, see " VRRP standard mode ."
• Load balancing mode—Extends the VRRP standard mode to distribute load across VRRP group
members. For more information, see "
VRRP load balancing mode ."
VRRP has two versions: VRRPv2 and VRRPv3. VRRPv2 supports IPv4 VRRP. VRRPv3 supports IPv4 VRRP
and IPv6 VRRP.