R21xx-HP FlexFabric 11900 MPLS Command Reference

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mpls ttl propagate
Use mpls ttl propagate to enable TTL propagation.
Use undo mpls ttl propagate to disable TTL propagation.
Syntax
mpls ttl propagate { public | vpn }
undo mpls ttl propagate { public | vpn }
Default
TTL propagation is enabled for public network packets and disabled for VPN packets.
Views
System view
Predefined user roles
network-admin
Parameters
public: Specifies public network packets.
vpn: Specifies VPN packets.
Usage guidelines
When TTL propagation is enabled, MPLS copies the IP TTL to the label TTL for packets entering the MPLS
network, and copies the label TTL to the IP TTL for packets leaving the MPLS network. If you enable TTL
propagation on both the ingress and egress, the IP tracert facility can show the real path in the MPLS
network.
When TTL propagation is disabled, MPLS sets the label TTL to 255 for packets entering the MPLS network,
and pops the label for packets leaving the MPLS network, without copying the label TTL value to the IP TTL.
The IP tracert facility cannot show the real path in the MPLS network.
After you enable or disable TTL propagation, execute the reset mpls ldp command to make the
configuration take effect. For more information about the reset mpls ldp command, see "LDP
commands."
W
ithin an MPLS network, TTL is always copied between the labels of an MPLS packet. The mpls ttl
propagate command affects only the propagation between IP TTL and label TTL.
HP recommends that you set the same TTL processing mode on all LSRs of an LSP.
To enable TTL propagation for a VPN, you must enable it on all PE devices in the VPN, so that you can
get the same traceroute result (hop count) from those PEs.
Examples
# Enable TTL propagation for VPN packets.
<Sysname> system-view
[Sysname] mpls ttl propagate vpn