LSP BFD is applicable to configured RSVP LSPs as well as mesh-p2p and one-hop-p2p auto-LSPs.
LSP BFD is configured on an RSVP-TE LSP, or on the primary or secondary path of an RSVP-TE LSP, under the bfd context at the LSP head end.
A BFD template must always be configured first. BFD is then enabled using the bfd-enable command.
config
router
mpls
lsp
bfd
[no] bfd-template <name>
[no] bfd-enable
[no] wait-for-up-timer <value>
exit
When BFD is configured at the LSP level, BFD packets follow the currently active path of the LSP.
The bfd-template provides the control packet timer values for the BFD session to use at the LSP head end. Because there is no LSP configuration at the tail end of an RSVP LSP, the BFD state machine at the tail end initially uses system-wide default parameters (the timer values are: min-tx: 1sec, min-rx: 1sec). The head end then attempts to adjust the control packet timer values when it transitions to the INIT state.
The BFD command wait-for-up-timer allows RSVP LSPs BFD sessions to come up duringMBB and switchover events when the current active path is not BFD degraded (that is, BFD is not down). It is only applicable in cases where failure-action failover-or-down is also configured (see Using LSP BFD for LSP Path Protection) and applies to the following:
a path undergoing MBB when BFD is up on the original path
the initial administrative enable of an LSP
signaling retry of non-standby secondary paths
The wait-for-up-timer command is configurable at either the lsp>bfd, primary>bfd, or secondary>bfd context. The value that the system uses is the one configured under the same context in which bfd-enable is configured. The wait-for-up-timer has a range of 1-60 seconds and a default of 4 seconds.
BFD is configured at the primary path level, as follows:
config
router
mpls
lsp
primary <path-name>
bfd
[no] bfd-template name <name>
[no] bfd-enable
[no] wait-for-up-timer <value>
exit
BFD is configured on both standby and non-standby secondary paths as follows:
config
router
mpls
lsp
secondary <path-name>
bfd
[no] bfd-template <name>
[no] bfd-enable
[no] wait-for-up-timer <value>
exit
BFD sessions are not established on these paths unless they are made active, unless failure-action failover-or-down is configured. See Using LSP BFD for LSP Path Protection. If failure-action failover-or-down is configured then the top three best-preference primary and standby paths (primary and up to two standby paths, or three standby paths if no primary is present) are programmed in the IOM, and BFD sessions are established on all of them.
It is not possible to configure LSP BFD on a secondary path or on P2MP LSPs.
LSP BFD at the LSP level and the path level is mutually exclusive. That is, if LSP BFD is already configured for the LSP then its configuration for the path is blocked. Likewise it cannot be configured on the LSP if it is already configured at the path level.
LSP BFD is supported on auto-LSPs. In this case, LSP BFD is configured on mesh-p2p and one-hop-p2p auto-LSPs using the LSP template, as follows:
Config
router
mpls
lsp-template template-name {mesh-p2p | one-hop-p2p}
bfd
[no] bfd-template name
[no] bfd-enable
exit