Step 1: Check That BGP Traffic Is Using the LSP

Purpose

At this level of the troubleshooting model, BGP and the LSP may be up, however BGP traffic might not be using the LSP to forward traffic.

Action

To verify that BGP traffic is using the LSP, enter the following JUNOS command-line interface (CLI) operational mode command from the ingress router:

user@host> traceroute hostname

Sample Output

user@R1> traceroute 100.100.6.1     

traceroute to 100.100.6.1 (100.100.6.1), 30 hops max, 40 byte packets

 1  10.1.13.2 (10.1.13.2)  0.653 ms  0.590 ms  0.543 ms

 2  10.1.36.2 (10.1.36.2)  0.553 ms !N  0.552 ms !N  0.537 ms !N

user@R6> traceroute 100.100.1.1     

traceroute to 100.100.1.1 (100.100.1.1), 30 hops max, 40 byte packets

 1  10.1.36.1 (10.1.36.1)  0.660 ms  0.551 ms  0.526 ms

 2  10.1.13.1 (10.1.13.1)  0.568 ms !N  0.553 ms !N  0.536 ms !N

What It Means

The sample output shows that BGP traffic is not using the LSP, consequently MPLS labels do not appear in the output. Instead of using the LSP, BGP traffic is using the interior gateway protocol (IGP) (IS-IS or OSPF, in the example network shown in Figure 24) to reach the BGP next-hop LSP egress address for R6 and R1. The JUNOS software default is to use LSPs for BGP traffic when the BGP next hop equals the LSP egress address.