Step 5: Verify MPLS Labels with the ping Command
Purpose
When you ping a specific LSP, you check that echo requests are sent over the LSP as MPLS packets. On the egress router (the router receiving the MPLS echo packets), you must configure the address
127.0.0.1/32on its loopback (lo0) interface. If this is not configured, the egress router does not have this forwarding entry and therefore simply drops the incoming MPLS pings and replies with "ICMP host unreachable" messages.Action
To verify MPLS labels, follow these steps:
- On the egress router, in configuration mode, go to the following hierarchy level:
[edit]user@host#edit interfaceslo0 unitnumber[edit]user@R6#edit interfaces lo0.0
- Configure the loopback (
lo0) interface with the following IP address:[editinterfaces lo0 unitnumber]user@host#set family inet address 127.0.0.1/32- Verify the configuration:
user@host#showuser@host#commit- On the ingress router, in operational mode, enter the following command to ping the egress router:
user@host>ping mpls rsvplsp-namedetailuser@R1>ping mpls rsvp R1-to-R6 detailSample Output 1
user@R1>ping mpls rsvp R1-to-R6 detailLSP R1-to-R6 - LSP has no active path, exiting.user@R6>ping mpls rsvp R6-to-R1 detailLSP R6-to-R1 - LSP has no active path, exiting.Sample Output 2
user@R1>traceroute 10.0.0.6traceroute to 10.0.0.6 (10.0.0.6), 30 hops max, 40 byte packets1 10.1.15.2 (10.1.15.2) 0.708 ms 0.613 ms 0.576 ms2 10.0.0.6 (10.0.0.6) 0.763 ms 0.708 ms 0.700 msuser@R1>ping mpls rsvp R1-to-R6 detailRequest for seq 1, to interface 69, label 100880Reply for seq 1, return code: Egress-okRequest for seq 2, to interface 69, label 100880Reply for seq 2, return code: Egress-okRequest for seq 3, to interface 69, label 100880Reply for seq 3, return code: Egress-okRequest for seq 4, to interface 69, label 100880Reply for seq 4, return code: Egress-okRequest for seq 5, to interface 69, label 100880Reply for seq 5, return code: Egress-ok--- lsping statistics ---5 packets transmitted, 5 packets received, 0% packet lossuser@R6>ping mpls rsvp R6-to-R1 detailRequest for seq 1, to interface 70, label 100864Reply for seq 1, return code: Egress-okRequest for seq 2, to interface 70, label 100864Reply for seq 2, return code: Egress-okRequest for seq 3, to interface 70, label 100864Reply for seq 3, return code: Egress-okRequest for seq 4, to interface 70, label 100864Reply for seq 4, return code: Egress-okRequest for seq 5, to interface 70, label 100864Reply for seq 5, return code: Egress-ok--- lsping statistics ---5 packets transmitted, 5 packets received, 0% packet lossWhat It Means
Sample Output 1 shows that the LSP does not have an active path to forward echo requests, indicating that the LSP is down.
Sample Output 2 is an example of output you should receive when the LSP is up and forwarding packets.