Configuring Association Between VRRP and BFD to Implement a Rapid Active/Standby Switchover

Context

When a VRRP group is faulty, the backup with the highest priority detects the fault and switches to the master after the Master_Down_Interval timer expires. The switchover period is at least 3s. During this switchover period, service traffic is still sent to the original master, causing loss of user traffic. In Figure 1, the VRRP group is associated with a BFD session on the backup. This association enables the BFD session to rapidly detect communication faults of the VRRP group. When the BFD session detects a fault, it notifies the VRRP group that the priority of the backup needs to be increased. Then an active/standby switchover is triggered immediately. This millisecond-level switchover reduces traffic loss.

When the fault is rectified, the priority of the backup is restored and the original master becomes the master again to forward traffic.

Only the S5720-EI, S5720-HI, S5720I-SI, S5720S-SI, S5720-SI, S5735-S, S5735S-S, S5735-S-I, S5730-HI, S5730S-EI, S5730-SI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6720S-SI, S6720-SI, S6730-H, S6730S-H, S6730-S, and S6730S-S support this function.
A VRRP group can be associated only with a static BFD session or a static BFD session with automatically negotiated discriminators.
The master and backup in the VRRP group must work in preemption mode. It is recommended that the preemption delay be 0 on the backup and non-zero on the master.
Multiple VRRP groups can monitor a BFD session, and a VRRP group can monitor a maximum of eight BFD sessions simultaneously.

Figure 1 Association between VRRP and BFD to implement a rapid active/standby switchover

Procedure

Configure a static BFD session or a static BFD session with automatically negotiated discriminators. For details, see Configuring Single-Hop BFD, Configuring Multi-Hop BFD, and Configuring Static BFD with Automatically Negotiated Discriminators.
Run system-view
The system view is displayed.
Run interface interface-type interface-number
The view of the interface on the backup where a VRRP group is configured is displayed.
(Optional) On an Ethernet interface, run undo portswitch
The interface is switched to Layer 3 mode.

By default, an Ethernet interface works in Layer 2 mode.

Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
Run vrrp vrid virtual-router-id track bfd-session { bfd-session-id | session-name bfd-configure-name } [ increased value-increased | reduced value-reduced ]
Association between VRRP and BFD is configured.

By default, a VRRP group is not associated with a BFD session.
When associating a VRRP group with a BFD session, note the following points:
- If session-name bfd-configure-name is specified, a VRRP group can be bound only to a static BFD session with automatically negotiated discriminators.
- If bfd-session-id is specified, the VRRP group can be bound only to a static BFD session.
- After the value by which the priority increases is set, ensure that the priority of the backup is higher than the priority of the master.
- When a BFD session is associated with VRRP, the system does not allow the associated BFD session to be deleted by default. To delete the associated BFD session, run the bfd session nonexistent-config-check disable command to disable the device from checking whether the associated BFD session is deleted.