LSP ping allows PE devices in the managed MPLS environment to send LSP pings to one another. LSP ping is available for Layer 2 and Layer 3 VPNs and is applicable to LDP (LDP-signaled) LSPs but not to TE (RSVP-signaled) LSPs.

The LSP ping functionality is defined in RFC 4379 and modeled after the ICMP ping utility that is documented in RFC 792. A source device sends an MPLS echo request packet to a destination device. Because the packet is forwarded over the LSP that is to be validated, the packet must use the label stack that is associated with that LSP. The MPLS echo reply is sent as an IP packet and forwarded using IP routing, MPLS switching, or a combination of both.