H3C Technologies H3C S12500 Series Switches - Manual (Page 144)

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VRRP application (taking IPv4-based VRRP for example)
Master/backup
In master/backup mode, only the master forwards packets. When the master fails, a new master is
elected from the backups. This mode requires only one VRRP group, in which each router holds a different
priority and the one with the highest priority becomes the master, as shown in Figure 33 .
Figure 33 VRRP in master/backup mode
Assume that Router A is the master and therefore can forward packets to external networks, whereas
Router B and Router C are backups and are thus in the state of listening. If Router A fails, Router B and
Router C elect for a new master to forward packets to hosts on the LAN.
Load sharing
More than one VRRP group can be created on an interface of a router to allow the router to be the master
of one VRRP group but a backup of another at the same time.
In load sharing mode, multiple routers provide services simultaneously. This mode requires two or more
VRRP groups, each of which comprises a master and one or more backups. The masters of the VRRP
groups are assumed by different routers, as shown in Figure 34 .