3Com S7902E, Configuration Manual

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Master IP : 10.1.1.2
The output information indicates that when there is a fault on the link between Switch A and Switch C,
the priority of Switch A decreases to 80. Switch A becomes the backup, and Switch B becomes the
master. Packets from Host A to Host B are forwarded through Switch B.
Configuring BFD for a VRRP Backup to Monitor the Master
Network requirements
z
As shown in Figure 1-3 , Switch A and Switch B belong to VRRP group 1, the virtual IP address of
which is 192.168.0.10.
z
The default gateway of the hosts in the LAN is 192.168.0.10. When Switch A works normally, the
hosts in the LAN access the external network through Switch A. When Switch A fails, the hosts in
the LAN access the external network through Switch B.
z
If BFD is not configured, when the master in a VRRP group fails, the backup cannot become the
master until the configured timeout timer expires. The timeout is generally three to four seconds
and therefore the switchover is slow. To solve this problem, VRRP uses BFD to probe the state of
the master. Once the master fails, the backup can become the new master within 1 second.
Figure 1-3 Network diagram for monitoring the master on the backup
Internet
Virtual router
Virtual IP address:
192.168.0.10
Vlan-int2
192.168.0.101/24
Vlan-int2
192.168.0.102/24
Switch A
Master
Switch B
Backup
L2 switch
VRRP packets
BFD probe packets
Configuration procedure
1) Configure VRRP on Switch A
<SwitchA> system-view
[SwitchA] interface vlan-interface 2
# Create VRRP group 1, and configure the virtual IP address 192.168.0.10 for the group. Set the priority
of Switch A in VRRP group 1 to 110.
[SwitchA-Vlan-interface2] vrrp vrid 1 virtual-ip 192.168.0.10