SR OS supports the configuration of a failure-action of type failover-or-down for SR-TE LSPs. The failure-action command is configured at the LSP level or in the LSP template. It can be configured whether S-BFD is applied at the LSP level or the individual path level.
For LSPs with a primary path and a standby or secondary path and failure-action of type failover-or-down:
A path is held in an operationally down state when its S-BFD session is down.
If all paths are operationally down, then the SR-TE LSP is taken operationally down and a trap is generated.
If S-BFD is enabled at the LSP or active path level, a switchover from the active path to an available path is triggered on failure of the S-BFD session on the active path (primary or standby).
If S-BFD is not enabled on the active path, and this path is shut down, then a switchover is triggered.
If S-BFD is enabled on the candidate standby or secondary path, then this path is only selected if S-BFD is up.
An inactive standby path with S-BFD configured is only considered as available to become active if it is not operationally down; for example, if the S-BFD session is up and all other criteria for it to become operational are true. It is held in an inactive state if the S-BFD session is down.
The system does not revert to the primary path nor start a reversion timer when the primary path is either administratively down or operationally down because the S-BFD session is not up or down for any other reason.
For LSPs with only one path and failure-action of type failover-or-down:
A path is held in an operationally down state when its S-BFD session is down.
If the path is operationally down, then the LSP is taken operationally down and a trap is generated.