A BFD session on an LSP is bootstrapped using LSP ping. LSP ping is used to exchange the local and remote discriminator values to use for the BFD session for a particular MPLS LSP or FEC.
SR OS supports the sending of periodic LSP ping messages on an LSP for which LSP BFD has been configured, as specified in RFC 5884. The ping messages are sent, along with the bootstrap TLV, at a configurable interval for LSPs on which bfd-enable has been configured. The default interval is 60 s, with a maximum interval of 300 s. The LSP ping echo request message uses the system IP address as the default source address. An alternative source address consisting of any routable address that is local to the node may be configured, and is used if the local system IP address is not routable from the far-end node.
SR OS does not take any action if a remote system fails to respond to a periodic LSP ping message. However, when the show>test-oam>lsp-bfd command is executed, it displays a return code of zero and a replying node address of 0.0.0.0 if the periodic LSP ping times out.
The periodic LSP ping interval is configured using the config>router>mpls>lsp>bfd>lsp-ping-interval seconds command.
The no lsp-ping-interval command reverts to the default of 60 s.
LSP BFD sessions are recreated after a high-availability switchover between active and standby CPMs. However, some disruption may occur to LSP ping because of LSP BFD.
At the tail end of an LSP, sessions are recreated on the standby CPM following an HA switchover. The following current information is lost from an active tools dump test-oam lsp-bfd tail display:
handle
seqNum
rc
rsc
Any new, incoming bootstrap requests are dropped until LSP BFD has become active. When LSP BFD has finished becoming active, new bootstrap requests are considered.