122Inspecting an MPLS TE tunnelOn an MPLS TE network, when an MPLS TE tunnel fails, the control plane cannot detect the failure orcannot do so in time. This brings difficulty to network maintenance. To detect MPLS TE tunnel failures intime and locate the failed node, the device provides the following mechanisms:• MPLS LSP ping• MPLS LSP tracert• BFD for an MPLS TE tunnel• Periodic tracert of an MPLS TE tunnelMPLS LSP pingMPLS LSP ping can be used to test the connectivity of an MPLS TE tunnel. At the ingress, it adds the labelof the tunnel into an MPLS echo request, and sends it along the MPLS TE tunnel to the egress. The ingressdetermines whether the MPLS TE tunnel is normal according to whether it can receive a reply from theegress.To test the connectivity of an MPLS TE tunnel, perform the following task in any view:Task CommandUse MPLS LSP ping to test theconnectivity of an MPLS TEtunnel.ping lsp [ -a source-ip | -c count | -exp exp-value | -h ttl-value | -m wait-time| -r reply-mode | -s packet-size | -t time-out | -v ] * te interface-typeinterface-numberMPLS LSP tracertMPLS LSP tracert can be used to locate errors of an MPLS TE tunnel. It sends MPLS echo requests to thenodes along the MPLS TE tunnel to be inspected, with the TTL increasing from 1 to a specific value. Eachnode along the MPLS TE tunnel will return an MPLS echo reply to the ingress due to TTL timeout. Thus, theingress can collect the information of each hop along the MPLS TE tunnel, so as to locate the failed node.You can also use MPLS LSP tracert to collect important information of each hop along the MPLS TE tunnel,such as the label allocated.To locate errors of an MPLS TE tunnel:Task Command RemarksUse MPLS LSP tracert to locateerrors of an MPLS TE tunnel.tracert lsp [ -a source-ip | -expexp-value | -h ttl-value | -rreply-mode |-t time-out ] * teinterface-type interface-numberAvailable in any viewConfiguring BFD for an MPLS TE TunnelYou can configure BFD for an MPLS TE tunnel to implement fast detection of the connectivity of the tunnel.After you configure BFD for an MPLS TE tunnel, a BFD session will be established between the ingressand egress of the tunnel, and the ingress will add the label for the tunnel into a BFD control packet,forward the BFD control packet along the tunnel, and determine the status of the tunnel according to the
