IP Router Configuration Command Reference
138 Router Configuration Guide
For IPv4 and IPv6 packets forwarded using a RFC 3107 label route in the global routing instance,
including 6PE, the all value of the command enables TTL propagation from the IP header into all labels
in the transport label stack. The none value reverts to the default mode which disables TTL propagation
from the IP header to the labels in the transport label stack. This command does not have a no version.
The TTL of the IP packet is always propagated into the RFC 3107 label itself, and this command only
controls the propagation into the transport labels, for example, labels of the RSVP or LDP LSP to
which the BGP label route resolves 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
will not follow the configuration described, but will follow the configuration to which the BGP label
route resolves.
RSVP LSP shortcut:
• configure router mpls shortcut-transit-ttl-propagate
LDP LSP shortcut:
• configure router ldp shortcut-transit-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 the listed RSVP or LDP LSP shortcut.
Default none
Parameters none — The TTL of the IP packet is not propagated into the transport label stack.
all — The TTL of the IP packet is propagated into all labels of the transport label stack.
lsr-label-route
Syntax ttl-propagate [all | none]
Context config>router>ttl-propagate
Description This command configures the TTL propagation for transit packets at a router acting as an LSR for a
BGP label route.
When an LSR swaps the BGP label for a ipv4 prefix packet, thus acting as a ABR, ASBR, or data-path
Route-Reflector (RR) in the base routing instance, or swaps the BGP label for a vpn-ipv4 or vpn-ipv6
prefix packet, thus acting as an inter-AS Option B VPRN ASBR or VPRN data path Route-Reflector
(RR), the all value of this command enables TTL propagation of the decremented TTL of the swapped
BGP label into all outgoing LDP or RSVP transport labels.
When an LSR swaps a label or stitches a label, it always writes the decremented TTL value into the
outgoing swapped or stitched label. What this feature controls is whether this decremented TTL value
is also propagated to the transport label stack pushed on top of the swapped or stitched label.
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