Introduction To Vrrp Group - 3Com 5500-EI PWR Install Manual

Introduction to VRRP Group

VRRP allows you to combine a group of LAN switches (including a master and several backups) into a
VRRP group. The VRRP group functions as a virtual router, forwarding packets as a gateway.
Figure 1-2 VRRP network diagram
Actual IP address
10.100.10.2/24
Master
Virtual IP address
10.100.10.1/24
10.100.10.7/24
Host 1
As shown in Figure
The virtual router (the VRRP group) has its own IP address (10.100.10.1 in the above figure).
The switches within the VRRP group must have their own IP addresses (such as 10.100.10.2 for
the master and 10.100.10.3 for the backup).
Hosts in the LAN use the IP address of the virtual router (that is, 10.100.10.1) as their default
gateway.
Hosts in the LAN only know the IP address of this virtual router, that is, 10.100.10.1, but not the
specific IP addresses 10.100.10.2 of the master and 10.100.10.3 of the backup.
If the master in the VRRP group goes down, the backups in the VRRP group will reelect a master by
priority. The backup with the highest priority functions as the new master to guarantee normal
communication between the hosts and the external networks.
Priority of a switch in a VRRP group
You can configure the priority of a switch in a VRRP group. A master is elected from these
VRRP-enabled switches by priority and the remaining switches are backups. The master in a VRRP
group is the one currently with the highest priority.
Switch priority ranges from 0 to 255 (a larger number indicates a higher switch priority). Note that only 1
through 254 are available to users. Switch priorities 0 and 255 are reserved for special uses and the IP
address owner respectively.
When a switch acts as the IP address owner, its priority is always 255. That is, if there is an IP address
owner in a VRRP group, it acts as the master as long as it works properly.
If two switches have the same VRRP priority, the one whose VLAN interface takes effect earlier
becomes the master.
Network
Actual IP address
10.100.10.3/24
Backup
Ethernet
10.100.10.8/24
Host 2
1-2, a VRRP group has the following features:
Virtual IP address
10.100.10.1/24
10.100.10.9/24
Host 3
1-2