Although the provisioning model and CLI syntax differ from that of a mesh LSP only by the absence of a prefix list, the actual behavior is quite different. When the above command is executed, the TE database keeps track of each TE link which comes up to a directly connected IGP neighbor which router-id is discovered. It then instructs MPLS to signals an LSP with a destination address matching the router-id of the neighbor and with a strict hop consisting of the address of the interface used by the TE link. Therefore, the auto-lsp command with the one-hop option results in one or more LSPs signaled to the IGP neighbor.
Only the router-id of the first IGP instance of the neighbor which advertises a TE link causes the LSP to be signaled. If subsequently another IGP instance with a different router-id advertises the same TE link, no action is taken and the existing LSP is kept up. If the router-id originally used disappears from the TE database, the LSP is kept up and is associated now with the other router-id.
The state of a one-hop LSP when signaled follows the following behavior:
If the interface used by the TE link goes down or BFD times out and the RSVP interface registered with BFD, the LSP path moves to the bypass backup LSP if the primary path is associated with one.
If while the one-hop LSP is UP, with the bypass backup path activated or not, the association of the TE-link with a router-id is removed in the TE databases, the one-hop LSP is torn down. This would be the case if the interface used by the TE link is deleted or if the interface is shutdown in the context of RSVP.
If while the LSP is UP, with the bypass backup path activated or not, the TE database loses the router-id, it performs two separate updates to MPLS module. The first one updates the loss of the TE link association which causes action (B) above for the one-hop LSP. The other update states router-id is no longer in TE database which causes MPLS to tear down all mesh LSPs to this router-id. A shutdown at the neighbor of the IGP instance which advertised the router-id causes the router-id to be removed from the ingress LER node immediately after the last IGP adjacency is lost and is not subject to age-out as for a non-directly connected destination router.
All other feature behavior, limitations, and statistics support are the same as for an auto-LSP of type mesh-p2p.