How to Verify Traffic Using the LSP in Junos

By Walter J. Goralski, Cathy Gadecki, and Michael Bushong from JUNOS OS For Dummies, 2nd Edition

Once you have configured static and explicit routes and linked them to an LSP, the easiest way to verify that traffic is traversing the path as you intended is by using the traceroute command. In the output, you want to verify that traffic is passing through the ERO (router 3). You also want to verify that MPLS labels are being used. Examine the topology to see the expected path:

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A network topology with a traceroute path.

Here’s how the traceroute output looks:

user@gateway> traceroute new-york 
traceroute to new-york (192.168.24.1), 30 hops max, 40 byte packets
 1  router5 (192.168.14.1)  0.869 ms  0.638 ms  0.536 ms
    MPLS Label-100004 CoS=0 TTL=1 S=1
 2  router4 (192.168.17.1)  0.869 ms  0.638 ms  0.536 ms
    MPLS Label-100004 CoS=0 TTL=1 S=1
 3  router3 (192.168.19.1)  24.968 ms  0.727 ms  0.363 ms
    MPLS Label-100004 CoS=0 TTL=1 S=1
 5  router1 (192.168.20.1)  24.968 ms  0.727 ms  0.363 ms
 6  new-york (192.168.24.1)  24.968 ms  0.727 ms  0.363 ms

Typically, it’s probably enough for you to verify that an MPLS label is in use. If you want to get more detailed, you can start to check the MPLS labels against the expected label values.