77• MPLS LSP tracert• BFD for LSPs• Periodic LSP tracertConfiguring MPLS LSP pingMPLS LSP ping is for checking the connectivity of an LSP. At the ingress, it adds the label for the FEC tobe inspected into an MPLS echo request, which then is forwarded along the LSP to the egress. The egressprocesses the request packet and returns an MPLS echo reply to the ingress. An MPLS echo reply carryinga success notification indicates that the LSP is normal, and an MPLS echo reply carrying an error codeindicates that the LSP has failed.Use the following command to test the connectivity of an LSP:Task Command RemarksUse MPLS LSP ping to check MPLSLSP connectivity.ping lsp [ -a source-ip | -c count |-exp exp-value | -h ttl-value | -mwait-time | -r reply-mode | -spacket-size | -t time-out | -v ] *ipv4 dest-addr mask-length[ destination-ip-addr-header ]Available in any view.When equal-cost LSPs existbetween the ingress node and theegress mode, you cannot use MPLSLSP ping to check the MPLS LSPconnectivity.Configuring MPLS LSP tracertMPLS LSP tracert is for locating LSP errors. It consecutively sends the MPLS echo requests along the LSP tobe inspected, with the TTL increasing from 1 to a specific value. Then, each hop along the LSP will returnan MPLS echo reply to the ingress due to TTL timeout. So, the ingress can collect information about eachhop along the LSP, so as to locate the failed node. You can also use MPLS LSP tracert to collect theimportant information about each hop along the LSP, such as the label allocated.Configuration prerequisites• Enable sending ICMP TTL exceeded messages on the intermediate devices between the sourcedevice and the destination device.• Enable sending ICMP destination unreachable messages on the destination device.• To display MPLS information during the tracert operation, enable support for ICMP extensions onthe source device and the intermediate devices.For more information about ICMP time exceeded messages, ICMP destination unreachable messages,and ICMP extensions for MPLS, see Layer 3—IP Services Configuration Guide.Configuration procedureUse the following command to locate errors of an LSP:
