A successful remote ping means that the routing-protocol sessions are operational between the two devices, but does not necessarily mean that the Label Distribution Protocol (LDP) sessions are operational between the devices. LDP is an MPLS signaling protocol for constructing LSPs.
In the majority of cases, an LDP session failure will be made known by a routing-protocol session failure, and therefore will be detected by remote ping. However, in certain situations, an LDP session can fail, while the routing-protocol session remains operational.
For this reason, MPLS Manager offers an on-demand LSP ping capability. LSP ping identifies LDP failures and misconfigurations.
LSP ping is described in Chapter 6, “LSP Ping Functionality.”
In addition, MPLS Manager is able to discover and monitor non-targeted LDP sessions. This capability works in parallel with on-demand LSP ping.