3Com MSR 50 Series Configuration Manual page 1973

Figure 584 Network diagram for VRRP
Host A
Host B
Host C
As shown in Figure
which has its own IP address. Hosts on the Ethernet use the virtual router as the
default gateway.
The router with the highest priority of the three routers is elected as the master
router to act as the gateway, and the other two are backup routers.
c
CAUTION:
The IP address of the virtual router can be either an unused IP address on the
■
segment where the standby group resides or the IP address of an interface on a
router in the standby group. In the latter case, the router is called the IP
address owner.
In a VRRP standby group, there can only be one IP address owner.
■
VRRP priority
VRRP determines the role (master or backup) of each router in the standby group
by priority. A router with a higher priority has more opportunity to become the
master.
VRRP priority is in the range of 0 to 255. A bigger number means a higher priority.
Priorities 1 to 254 are configurable. Priority 0 is reserved for special uses and
priority 255 for the IP address owner. When a router acts as the IP address owner,
its priority remains 255 and cannot be configured. That is, if there is an IP address
owner in a standby group, it acts as the master as long as it works properly.
Working mode
A router in a standby group can work in one of the following two modes:
Non-preemption mode
■
Once a router in the standby group becomes the master, it stays as the master as
long as it operates normally, even if a backup router is assigned a higher priority
later.
Preemption mode
■
Virtual router
Router A
Router B
Network
Router C
584, Router A, Router B, and Router C form a virtual router,
Introduction to VRRP 1973