BFD High Availability Support
BFD is deployed in the stacking setup where units take up active, standby, and member
roles, as illustrated in the following figure. When a failover occurs and the active
unit fails or goes through a switchover, the standby unit takes over as active. Therefore,
BFD-enabled routes are available for forwarding both during and post switchover.
Note: BFD session packets are generated in the member unit and not on the active unit.
BFD backs up and syncs session information from the active unit to the standby unit in the following cases:
- An application initiates a new BFD session.
- An existing BFD session is changed or updated.
- A new application is configured for an existing BFD session.
- An existing BFD session is unconfigured or removed.
During a switchover, BFD sessions are changed to an admin-down state, and are newly booted up post switchover. After a switchover or failover, the BFD sessions are reconciled to the new active unit. This can result in the removal of stale sessions or the moving of existing sessions to another port. BFD applications registered with BFD at the peer level will are not impacted and no re-convergence is needed.