H3C Technologies H3C S12500-X Series Switches - Manual (Page 89)

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Total number of virtual routers : 1
Interface Vlan-interface2
VRID : 1 Adver Timer : 500
Admin Status : Up State : Backup
Config Pri : 110 Running Pri : 80
Preempt Mode : Yes Delay Time : 5
Become Master : 2200ms left
Auth Type : Simple Key : ******
Virtual IP : 10.1.1.10
Master IP : 10.1.1.2
VRRP Track Information:
Track Object : 1 State : Negative Pri Reduced : 30
# Display detailed information about VRRP group 1 on Switch B when a fault is on the link between
Switch A and Switch C.
[SwitchB-Vlan-interface2] display vrrp verbose
IPv4 Virtual Router Information:
Running Mode : Standard
Total number of virtual routers : 1
Interface Vlan-interface2
VRID : 1 Adver Timer : 500
Admin Status : Up State : Master
Config Pri : 100 Running Pri : 100
Preempt Mode : Yes Delay Time : 5
Auth Type : Simple Key : ******
Virtual IP : 10.1.1.10
Virtual MAC : 0000-5e00-0101
Master IP : 10.1.1.2
The output shows that when a fault is 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
As shown in Figure 22 , Switch A and Switch B belong to VRRP group 1, whose virtual IP address is
192.168.0.10.
The default gateway of the hosts in the LAN is 192.168.0.10. When Switch A works correctly, 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.
If the master in a VRRP group fails and BFD is not configured, the backup cannot become the master until
the configured timeout timer expires. The timeout is usually 3 to 4 seconds, which is a long delay for most
applications. 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 in milliseconds.