H3C Technologies H3C SR8800 - Manual (Page 50)

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Configuring VRRP
NOTE:
•
The term router in this document refers to both routers and Layer 3 switches.
• The interfaces that VRRP involves can be only Layer 3 Ethernet interfaces/subinterfaces, VLAN
interfaces, Layer 3 aggregate interfaces/subinterfaces, and RPR logical interfaces unless otherwise
specified.
• VRRP cannot be configured on an interface of an aggregation group.
VRRP overview
Typically, as shown in Figure 10 , you can configure a default route with the gateway as the next hop for
every host on a network segment. All packets destined to other network segments are sent over the
default route to the gateway, which then forwards the packets. However, when the gateway fails, all the
hosts that use the gateway as the default next-hop router fail to communicate with external networks.
Figure 10 LAN networking
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. Routers in the
VRRP group elect a master through the VRRP election mechanism to act as a gateway, and hosts on a
LAN only need to configure the virtual router as their default network gateway.
VRRP is an error-tolerant protocol, which improves the 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 prevent network interruption due to a single link failure.
Gateway
Network
Host A
Host B
Host C