For IPv4 and IPv6 packets forwarded using a RFC 3107 label route in the global routing instance, including label-IPv6, the following command specified with the all value enables TTL propagation from the IP header into all labels in the transport label stack:
config router ttl-propagate label-route-local [none | all]
config router ttl-propagate label-route-transit [none | all]
The none value reverts to the default mode which disables TTL propagation from the IP header to the labels in the transport label stack.
These commands do not have a no version.
The TTL of the IP packet is always propagated into the RFC 3107 label itself. The commands only control the propagation into the transport labels, for example, the labels of the RSVP or LDP LSP which the BGP label route resolves to and which are pushed on top of the BGP label.
If the BGP peer advertised the implicit-null label value for the BGP label route, the TTL propagation does not follow the configuration described, but follows the configuration to which the BGP label route resolves:
RSVP LSP shortcut:
configure router mpls shortcut-transit-ttl-propagate
configure router mpls shortcut-local-ttl-propagate
LDP LSP shortcut:
configure router ldp shortcut-transit-ttl-propagate
configure router ldp shortcut-local-ttl-propagate
This feature does not impact packets forwarded over BGP shortcuts. The ingress LER operates in uniform mode by default and can be changed into pipe mode using the configuration of TTL propagation for RSVP or LDP LSP shortcut.