A method for checking connectivity between a first device and a second device on a bidirectional Label Switched Path LSP, includes the first device sends, to the second device, an echo request including a reply mode and a return address, the reply mode requesting an echo reply to be delivered through backward LSP, and the return address being the unique ID of the first device; the first device receives an echo reply from the second device, the echo reply including the unique ID of the first device and return code related to connectivity of the backward LSP; and the first device correlates the echo reply with the echo request to verify connectivity between the two devices on the bidirectional Label Switched Paths.