3Com Switch 4800G 24-Port Configuration Manual page 1075

As shown in Figure 319, Switch A, Switch B, and Switch C form a virtual router,
which has its own IP address. Hosts on the Ethernet use the virtual router as the
default gateway.
The switch with the highest priority of the three switches is elected as the master
switch to act as the gateway, and the other two are backup switches.
c
CAUTION:
The IP address of the virtual router can be either an unused IP address on the
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segment where
the standby group resides or the IP address of an interface on a switch in the
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standby group. In the latter case, the switch is called the IP address owner.
In a VRRP standby group, there can only be one IP address owner.
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VRRP priority
VRRP determines the role (master or backup) of each switch in the standby group
by priority. A switch 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 switch acts as the IP address owner,
its priority remains 255. 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 switch in a standby group can work in one of the following two modes:
Non-preemption mode
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Once a switch in the standby group becomes the master, it stays as the master as
long as it operates normally, even if a backup switch is assigned a higher priority
later.
Preemption mode
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Once a backup switch finds its priority higher than that of the switch acting as the
master, it sends VRRP advertisements to start a new master switch election in the
standby group and becomes the master. Accordingly, the original master switch
becomes a backup.
Authentication mode
VRRP provides two authentication modes:
simple: Simple text authentication
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You can adopt the simple text authentication mode in a network facing possible
security problems. A switch sending a packet fills the authentication key into the
packet, and the switch receiving the packet compares its local authentication key
with that of the received packet. If the two authentication keys are the same, the
received VRRP packet is considered real and valid; otherwise, the received packet is
considered an invalid one.
Introduction to VRRP 1075