Understanding MPLS TTL Processing
This chapter contains configurations for MPLS-TTL-Processing. It also provides an overview of MPLS-TTL-Processing concepts.
Overview
This feature performs ‘Time To Live’ (TTL) processing for Multi-Protocol Label Switching (MPLS) packets. The TTL processing is decided by the model chosen by you. This feature provides TTL processing of MPLS packets on ingress, egress, and intermediate routers. TTL processing is compliant with RFC 3443.
The details of TTL processing vary with the tunnel model that is configured for TTL processing. The incoming and outgoing TTL of the packet is determined by the configured tunnel model. Two Models are supported, pipe model and uniform model. Pipe model is default model, where MPLS header TTL Value wont get propagated to IP header.
To know more about uniform model and pipe model, refer chapter MPLS DiffServ Configuration.
Topology
TTL Processing Topology
Configuration
PE1
PE1#configure terminal | Enter configure mode |
PE1(config)#interface lo | Enter interface mode. |
PE1(config-if)#ip address 1.1.1.1/32 | Configure IP address for the loopback address |
PE1(config-if)#exit | Exit interface mode |
PE1(config)#interface xe6 | Specify the interface (xe6)to be configured |
PE1(config-if)#ip address 10.10.10.1/24 | Configure IP address for the interface |
PE1(config-if)#no shutdown | Administratively bringing up the interface |
PE1(config-if)#exit | Exit interface mode |
PE1(config)#router ospf 100 | Configure the routing process and specify the Process ID (100) |
PE1(config-router)#network 10.10.10.0/24 area 0 PE1(config-router)#network 1.1.1.1/32 area 0 | Define the interface on which OSPF runs and associate the area ID(0)with the interface |
PE1(config-router)#exit | Exit configure mode |
PE1(config)#router ldp | Enter router mode for LDP |
PE1(config-router)#exit | Exit router mode for LDP |
PE1(config)#interface xe6 | Specify the interface (xe6)to be configured |
PE1(config-if)#label-switching | Enabling label switching capability on router |
PE1(config-if)#enable-ldp ipv4 | Enabling ldp on interface |
PE1(config-if)#exit | Exit interface mode |
PE1(config)#exit | Exit configure mode |
P
P#configure terminal | Enter configure mode. |
P(config)#interface lo | Enter interface mode. |
P(config-if)#ip address 2.2.2.2/32 | Configure IP address for the loopback address |
P(config-if)#exit | Exit interface mode |
P(config)#interface xe6 | Specify the interface (xe6)to be configured |
P(config-if)#ip address 10.10.10.2/24 | Configure IP address for the interface |
P(config-if)#no shutdown | Administratively bringing up the interface |
P(config)#interface xe1 | Specify the interface (xe1)to be configured |
P(config-if)#ip address 20.20.20.1/24 | Configure IP address for the interface |
P(config)#router ospf 100 | Configure the routing process and specify the Process ID (100) |
P(config-router)#network 10.10.10.0/24 area 0 P(config-router)#network 20.20.20.0/24 area 0 P(config-router)#network 2.2.2.2/32 area 0 | Define the interface on which OSPF runs and associate the area ID (0)with the interface |
P(config-router)#exit | Exit router mode |
P(config)#router ldp | Enter router mode for LDP |
P(config-router)#exit | Exit router mode for LDP |
P(config)#interface xe6 | Specify the interface (xe6)to be configured |
P(config-if)#label-switching | Enabling label switching capability on router |
P(config-if)#enable-ldp ipv4 | Enabling ldp on interface |
P(config)#interface xe1 | Specify the interface (xe1)to be configured |
P(config-if)#label-switching | Enabling label switching capability on router |
P(config-if)#enable-ldp ipv4 | Enabling ldp on interface |
P(config-if)#exit | Exit interface mode |
P(config)#exit | Exit configure mode |
PE2
PE2#configure terminal | Enter configure mode. |
PE2(config)#interface lo | Enter interface mode. |
PE2(config-if)#ip address 3.3.3.3/32 | Configure IP address for the loopback address |
PE2(config-if)#exit | Exit interface mode |
PE2(config)#interface xe1 | Specify the interface (xe1)to be configured |
PE2(config-if)#ip address 20.20.20.2/24 | Configure IP address for the interface |
PE2(config-if)#no shutdown | Administratively bringing up the interface |
PE2(config-if)#exit | Exit interface mode |
PE2(config)#router ospf 100 | Configure the routing process and specify the Process ID (100) |
PE2(config-router)#network 20.20.20.0/24 area 0 PE2(config-router)#network 3.3.3.3/32 area 0 | Define the interface on which OSPF runs and associate the area ID (0)with the interface |
PE2(config)#router ldp | Enter router mode for LDP |
PE2(config-router)#exit | Exit router mode for LDP |
PE2(config)#interface xe1 | Specify the interface (xe1)to be configured |
PE2(config-if)#label-switching | Enabling label switching capability on router |
PE2(config-if)#enable-ldp ipv4 | Enabling ldp on interface |
PE2(config-if)#exit | Exit interface mode |