H3C Technologies H3C SecPath F1000-E - Manual (Page 4)

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Figure 2 Network diagram for VRRP
Host A
Host B
Host C
Router A
Router B
Router C
Virtual router
Network
As shown in
Figure 2 , Router A, Router B, and Router C form a virtual router, which has its own IP address.
Hosts on the Ethernet use the virtual router as the default gateway.
The router with the highest priority among the three routers is elected as the master to act as the gateway,
and the other two are backups.
NOTE:
•
The IP address of the virtual router can be either an unused IP address on the segment 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.
• Only one IP address owner can be configured for a VRRP group.
• Status of a router in a VRRP group includes master, backup, and initialize.
VRRP priority
VRRP determines the role (master or backup) of each router in a VRRP group by priority. A router with a
higher priority is more likely to become the master.
VRRP priority is in the range of 0 to 255. The greater the number, the higher the 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 running priority is always 255. That is, the IP address
owner in a VRRP group acts as the master as long as it works properly.
Working mode
A router in a VRRP group works in either of the following two modes:
• Non-preemptive mode
When a router in the VRRP group becomes the master, it stays as the master as long as it operates
normally, even if a backup is assigned a higher priority later.
• Preemptive mode
When a backup finds its priority higher than that of the master, the backup sends VRRP advertisements
to start a new master election in the VRRP group and becomes the master. Accordingly, the original
master becomes a backup.