OSPF to CE Configuration Example

In this example, the network shown in the diagram below is configured for OSPF to forward routes between the networks attached to the CE routers and the PE routers. IBGP is used to forward routes between the PE routers and an LSP tunnel is configured across the MPLS domain. The diagram below contains all of the network addresses and AS numbers required to perform this configuration. The configurations are shown for only the CE 1, CE 5, PE 1 and PE 5 routers, which demonstrates what is required to make VPN1 work. The configurations for VPN2, VPN3, and VPN 4 would essentially be the same.

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OSPF to CE network example

CE 1 Configuration

This configuration example describes what is required to operate the CE 1 router in the diagram above. In this example, a static route is configured between the external network (10.1.2.0/24) and the loopback interface. OSPF is configured to redistribute static routes between the CE 1 router and the attached interface of PE 1. 

      device(config)# interface loopback 1
device(config-lbif-1)# ip address 10.33.33.1/32 
device(config-lbif-1)# exit

device(config)# ip route 10.1.2.0/24 10.33.33.1
device(config)# router ospf
device(config-ospf-router)# area 1
device(config-ospf-router)# redistribute static
device(config-ospf-router)# exit

device(config)# interface ethernet 0/1
device(config-if-e10000-0/1)# ip address 10.33.33.2
device(config-if-e10000-0/1)# ip ospf area 1
device(config-if-e10000-0/1)# exit

CE 5 Configuration

This configuration example describes what is required to operate the CE 5 router in the diagram above. In this example, a static route is configured between the external network (10.1.3.0/24) and the loopback interface. OSPF is configured to redistribute static routes between the CE 5 router and the attached interface of PE 4. 

      device(config)# interface loopback 1
device(config-lbif-1)# ip address 10.33.36.1/32 
device(config-lbif-1)# exit

device(config)# ip route 10.1.3.0/24 10.33.36.1
device(config)# router ospf
device(config-ospf-router)# area 1
device(config-ospf-router)# redistribution static
device(config-ospf-router)# exit

device(config)# interface ethernet 0/1
device(config-if-e10000-0/1)# ip address 10.33.36.2
device(config-if-e10000-0/1)# ip ospf area 1
device(config-if-e10000-0/1)# exit

PE 1 Configuration

This configuration example describes what is required to operate the PE 1 router in the diagram above. In this example, the VRF VPN1 is created with a unique route descriptor consisting of the BGP AS number (1) and a random other number (2), and route targets are set for import and export. The VRF (VPN1) is defined on the interface that connects to CE 1. OSPF is configured on the VRF named VPN1 to exchange routes with CE 1 and to redistribute routes from across the MPLS domain.

IBGP with extended community attributes is configured between PE 1 and PE 4. The OSPF area is specified as 0 and MPLS is set up for OSPF traffic engineering. In addition, MPLS is configured with a signalled LSP named "tunnel1" to PE 1. 

      device(config)# interface loopback 1
device(config-lbif-1)# ip address 10.2.2.1/24
device(config-lbif-1)# ip ospf area 0
device(config-lbif-1)# exit

device(config)# vrf VPN1
device(config-vrf-vpn1)# rd 1:1
device(config-vrf-vpn1)# route-target export 100:1 
device(config-vrf-vpn1)# route-target import 100:2
device(config-vrf-vpn1)# exit-vrf

device(config)# router bgp 
device(config-bgp)# local-as 1
device(config-bgp)# neighbor 10.2.2.2 remote-as 1
device(config-bgp)# neighbor 10.2.2.2 update-source loopback 1
device(config-bgp)# address-family vpnv4 unicast
device(config-bgp-vpnv4u)# neighbor 10.2.2.2 activate
device(config-bgp)# address-family ipv4 unicast vrf VPN1
device(config-bgp-ipv4u-vrf)# redistribute ospf
device(config-bgp-ipv4u-vrf)# exit

device(config)# router ospf vrf VPN1
device(config-ospf-router)# area 1
device(config-ospf-router)# redistribute bgp
device(config-ospf-router)# exit

device(config)# router ospf
device(config-ospf-router)# area 0
device(config-ospf-router)# exit

device(config)# interface ethernet 0/2
device(config-if-e10000-0/2)# ip address 10.33.34.1/24
device(config-if-e10000-0/2)# ip ospf area 0
device(config-if-e10000-0/2)# exit

device(config)# router mpls
device(config-mpls)# policy 
device(config-mpls-policy)# traffic-engineering ospf
device(config-mpls)# mpls-interface eth 0/2
device(config-mpls)# lsp tunnel1
device(config-mpls-lsp-tunnel1)# to 10.2.2.2
device(config-mpls-lsp-tunnel1)# enable
device(config-if-e10000-0/2)# exit

device(config)# interface ethernet 0/1
device(config-if-e10000-0/1)# vrf forwarding VPN1
device(config-if-e10000-0/1)# ip address 10.33.33.3/24
device(config-if-e10000-0/1)# ip ospf area 1
device(config-if-e10000-0/1)# exit

PE 4 Configuration

This configuration example describes what is required to operate the PE 4 router in the diagram above. In this example, the VRF VPN1 is created with a unique route descriptor consisting of the BGP AS number (1) and a random other number (2), and route targets are set for import and export. The VRF (VPN1) is defined on the interface that connects to CE 5. OSPF is configured on the VRF named VPN1 to exchange routes with CE 5 and to redistribute routes from across the MPLS domain. 

      device(config)# interface loopback 1
device(config-lbif-1)# ip address 10.2.2.2/32 
device(config-lbif-1)# ip ospf area 1
device(config-lbif-1)# exit

device(config)# vrf VPN1
device(config-vrf-vpn1)# rd 2:1
device(config-vrf-vpn1)# route-target export 100:2
device(config-vrf-vpn1)# route-target import 100:1
device(config-vrf-vpn1)# exit-vrf

device(config)# router bgp 
device(config-bgp)# local-as 1
device(config-bgp)# neighbor 10.2.2.1 remote-as 1
device(config-bgp)# neighbor 10.2.2.1 update-source loopback 1
device(config-bgp)# address-family vpnv4 unicast
device(config-bgp-vpnv4u)# neighbor 10.2.2.1 activate
device(config-bgp)# address-family ipv4 unicast vrf VPN1
device(config-bgp-ipv4u-vrf)# redistribute ospf
device(config-bgp-ipv4u-vrf)# exit

device(config)# router ospf vrf VPN1
device(config-ospf-router)# area 1
device(config-ospf-router)# redistribute bgp
device(config-ospf-router)# exit

device(config)# router ospf
device(config-ospf-router)# area 0
device(config-ospf-router)# exit

device(config)# interface ethernet 0/2
device(config-if-e10000-0/2)# ip ospf area 0
device(config-if-e10000-0/2)# ip address 10.33.35.1/24
device(config-if-e10000-0/2)# exit

device(config)# router mpls
device(config-mpls)# policy 
device(config-mpls-policy)# traffic-engineering ospf
device(config-mpls)# mpls-interface eth 0/2
device(config-mpls)# lsp tunnel1
device(config-mpls-lsp-tunnel1)# to 10.2.2.1
device(config-mpls-lsp-tunnel1)# enable
device(config-mpls-lsp-tunnel1)# exit

device(config)# interface ethernet 0/1
device(config-if-e10000-0/1)# vrf forwarding VPN1
device(config-if-e10000-0/1)# ip address 10.33.36.3/24
device(config-if-e10000-0/1)# ip ospf area 1
device(config-if-e10000-0/1)# exit
9036674-01 Rev AA