This document defines extensions to the failure-detection protocol for Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs) known as "LSP Ping" that allow selection of the LSP to use for the echo reply return path. Enforcing a specific return path can be used to verify bidirectional connectivity and also increase LSP ping robustness. It may also be used by Bidirectional Forwarding Detection (BFD) for MPLS bootstrap signaling thereby making BFD for MPLS more robust.