MPLS TTL Handling

By default the IP TTL value is copied into the MPLS header when a packet enters the MPLS network. To disable this behavior there two options. The first is proprietary to Junos and is only required on the ingress router at the head end of the transit LSP. The feature can be configured at a global MPLS level for all ingress LSPs or configured at an LSP level for primary or secondary LSPs. The feature is carried as a proprietary object within RSVP and is therefore only available on RSVP signalled LSPs.

protocols {
     mpls {
          label-switched-path R1_to_R4 {
               no-decrement-ttl;
          }
     }
}
The second option is interoperable with other vendors and is required to be configured at the global level on all LSRs. It supports both LDP and RSVP LSPs.
protocols {
     mpls {
          no-propagate-ttl;
     }
}

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