H3C Technologies H3C S12500-X Series Switches - Manual (Page 46)

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Configuring VRRP
The term "interface" in VRRP collectively refers to Layer 3 interfaces, including VLAN interfaces and Layer
3 Ethernet interfaces. You can set an Ethernet port as a Layer 3 interface by using port link-mode route
(see Layer 2—LAN Switching Configuration Guide).
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 12 , when the default gateway fails,
no hosts can communicate with external networks.
Figure 12 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 takes over. The switchover is complete without causing dynamic route recalculation, route
re-discovery, gateway reconfiguration on the hosts, or traffic interruption.
VRRP operates in standard mode implemented based on RFCs. For more information, see "
VRRP
standard mode ."