IP Router Configuration Command Reference
140 Router Configuration Guide
When a packet is received in a VPRN context but is looked up in the Global Routing Table (GRT), for
example, leaking to GRT is enabled, the behavior of the TTL propagation is governed by the RSVP or
LDP shortcut configuration when the matching routing is a LSP shortcut route. It is governed by the
BGP label route configuration when the matching route is a RFC 3107 label route or a 6PE route.
When a packet is received on one VPRN instance and is redirected using Policy Based Routing (PBR)
to be forwarded in another VPRN instance, the TTL propagation is governed by the configuration of
the outgoing VPRN instance.
Default vc-only
Parameters none — The TTL of the IP packet is not propagated into the VC label or labels in the transport
label stack
vc-only — The TTL of the IP packet is propagated into the VC label and not into the labels in the
transport label stack.
all — The TTL of the IP packet is propagated into the VC label and all labels in the transport label
stack.
vprn-transit
Syntax vprn-transit [all | vc-only | none]
Context config>router>ttl-propagate
Description This command configures the TTL propagation for in transit packets which are forwarded over a
MPLS LSPs in all VPRN service contexts. For vpn-ipv4 and vpn-ipv6 packets forwarded in the context
of all VPRN services in the system, including 6VPE packets, the all value of the command enables
TTL propagation from the IP header into all labels in the stack:
The user can enable the TTL propagation behavior separately for locally generated packets by CPM
(vprn-local) and for user and control packets in transit at the node (vprn-transit).
The vc-only value reverts to the default behavior by which the IP TTL is propagated into the VC label
but not to the transport labels in the stack. The user can explicitly set the default behavior by
configuring the vc-only value. This command does not have a no version.
The value none allows the user to disable the propagation of the IP TTL to all labels in the stack,
including the VC label. This is needed for a transparent operation of UDP trace-route in VPRN inter-
AS option B such that the ingress and egress ASBR nodes are not traced.
The user can override the global configuration within each VPRN service instance using the following
commands:
• config service vprn ttl-propagate local [inherit | none | vc-only | all]
• config service vprn ttl-propagate transit [inherit | none | vc-only | all]
The default behavior for a given VPRN instance is to inherit the global configuration for the same
command. The user can explicitly set the default behavior by configuring the inherit value.
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