H3C Technologies H3C S12500-X Series Switches - Manual (Page 92)

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# Enable VRRP state debugging and BFD event debugging on Switch B.
terminal debugging
terminal monitor
debugging vrrp state
debugging bfd event
# When Switch A fails, the following output is displayed on Switch B.
*Dec 17 14:44:34:142 2012 SwitchB BFD/7/EVENT: Send sess-down Msg,
[Src:192.168.0.102,Dst:192.168.0.101,Vlan-interface2,Echo], instance:0, protocol:Track
*Dec 17 14:44:34:144 2012 SwitchB VRRP/7/DebugState: IPv4 Vlan-interface2 | Virtual Router
1 : Backup --> Master reason: The status of the tracked object changed
# Display detailed information about the VRRP group on Switch B.
display vrrp verbose
IPv4 Virtual Router Information:
Running Mode : Standard
Total number of virtual routers : 1
Interface Vlan-interface2
VRID : 1 Adver Timer : 100
Admin Status : Up State : Master
Config Pri : 100 Running Pri : 100
Preempt Mode : Yes Delay Time : 0
Auth Type : None
Virtual IP : 192.168.0.10
Virtual MAC : 0000-5e00-0101
Master IP : 192.168.0.102
VRRP Track Information:
Track Object : 1 State : Negative Switchover
The output shows that when BFD detects that Switch A fails, it notifies VRRP through the Track module to
change the status of Switch B to master without waiting for a period three times the advertisement interval.
This ensures that a backup can quickly preempt as the master.
Configuring BFD for the VRRP master to monitor the uplinks
Network requirements
As shown in Figure 23 , 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 detects that the uplink is down through BFD, it decreases its priority so that Switch B can
preempt as the master, ensuring that the hosts in the LAN can access the external network through Switch
B.