lspv mpls-lsp-ping echo enable

Usage Scenario

The ping and trace tests use ICMP packets to locate faulty nodes on a forwarding path. When an LSP fails, IP forwarding-based ICMP packets cannot be used to detect the faulty node.

In this case, the ping lsp and tracert lsp command can be used to locate the faulty node on the LSP. These commands use MPLS Echo Request and MPLS Echo Reply packets to detect the connectivity of an LSP. Both MPLS Echo Request and MPLS Echo Reply packets are encapsulated into UDP packets and transmitted through port 3503. The receiver distinguishes MPLS Echo Request and MPLS Echo Reply packets based on the port number. An MPLS Echo Request packet carries FEC information to be detected, and is sent along the same LSP as other packets with the same FEC information. In this manner, the connectivity of the LSP is checked. MPLS Echo Request packets are transmitted to the destination through MPLS, whereas MPLS Echo Reply packets are transmitted to the source through IP.

For network security or management, you can run the lspv mpls-lsp-ping echo enable command to enable a device to respond to MPLS Echo Request packets or run the undo lspv mpls-lsp-ping echo enable command to disable the device from responding to MPLS Echo Request packets. This function is implemented by enabling or disabling port 3503. By default, port 3503 is enabled.

After you run the ping lsp and tracert lsp command to detect the connectivity of an LSP, you are advised to run the undo lspv mpls-lsp-ping echo enable command to disable the device from responding to MPLS Echo Request packets to avoid occupation of system resources.

Precautions

If you run the undo lspv mpls-lsp-ping echo enable command to disable a device from responding to MPLS Echo Request packets, this device does not respond to the ping lsp and tracert lsp command. As a result, the ping or trace test with the address of the device as the destination address times out.