Perform the following steps to configure MPLS QoS pipe mode on both the ingress LER and the MPLS router that pops the label (either the penultimate LSR or the egress LER).
Note
If you do not configure the MPLS router that pops the label, the value in the packet‘s MPLS TTL field is copied into the packet‘s IP TTL field. This value could be as high as 255.
-
In privileged EXEC mode, enter global configuration mode.
device# configure terminal
-
Enter router MPLS mode.
device(config)# router mpls
-
Enter policy mode.
device(config-router-mpls)# policy
-
Change the MPLS QoS mode to pipe.
device(config-router-mpls-policy)# qos-ttl-mode pipe
The ingress LER places a value of 255 into the packet‘s MPLS TTL field, regardless of the TTL value in the packet‘s IP header. The packet‘s IP TTL value is decremented twice; once at the ingress LER and once at the egress LER. The entire MPLS domain, regardless of the number of transit LSR hops, counts as two hops for the IP TTL value.
The mode changes are applied for newly created tunnels. They are not reapplied to an existing tunnel.
-
If required, reset the default MPLS QoS mode of uniform.
device(config-router-mpls-policy)# no qos-ttl-mode
You can also use the
qos-ttl-mode uniform command.
Example
The following configuration shows the previous steps.
device# configure terminal
device(config)# router mpls
device(config-router-mpls)# policy
device(config-router-mpls-policy)# qos-ttl-mode pipe
device(config-router-mpls-policy)# no qos-ttl-mode
