MPLS Sampling Behavior

This section describes the behavior when MPLS sampling is used on egress interfaces in various scenarios (label pop or swap) on provider routers (P routers). For more information on configuration and background specific to MPLS applications, see the JUNOS MPLS Applications Configuration Guide.

1. You configure MPLS sampling on an egress interface on the P router and configure an MPLS flow aggregation template. The route action is label pop because penultimate hop popping (PHP) is enabled.

   Previously, IPv4 packets (only) would have been sent to the PIC for sampling even though you configured MPLS sampling. No flows should be created, with the result that the parser fails.

   With the current capability of applying MPLS templates, MPLS flows are created.

2. As in the first case, you configure MPLS sampling on an egress interface on the P router and configure an MPLS flow aggregation template. The route action is label swap and the swapped label is 0 (explicit null).

   Resulting behavior is that MPLS packets are sent to PIC. The flow being sampled corresponds to the label before the swap.

3. You configure a Layer 3 VPN network, in which a customer edge router (CE-1) sends traffic to a provider edge router (PE-A), through the P router, to a similar provider edge router (PE-B) and customer edge router (CE-2) on the remote end.

   Resulting behavior is that you cannot sample MPLS packets on the PE-A to P router link.

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