EBGP for Route Exchange

To exchange routes, a BGP neighbor must be configured on both CE and PE routers. In the diagram shown below, the CE 1 router is configured to exchange routes with the PE 1 router and the CE 5 router is configured to exchange routes with the PE 4 router.

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EBGP to CE network example

EBGP to CE network example

In the example shown in the diagram above, the network is configured to use EBGP 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 above 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.

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. EBGP is configured between CE 1 and PE 1, and the static route is redistributed through this connection.

device(config)# ip route 10.1.2.0/24 10.33.33.1
device(config)# router bgp
device(config-bgp)# local-as 2
device(config-bgp)# neighbor 10.33.33.3 remote-as 1
device(config-bgp)# redistribute static
device(config-bgp)# exit
device(config)# interface ethernet 0/1
device(config-if-e10000-0/1)# ip address 10.33.33.2/24
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. EBGP is configured between CE 5 and PE 4, and the static route is redistributed through this connection.

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 bgp
device(config)# local-as 3
device(config-bgp)# neighbor 10.33.36.3 remote-as 1
device(config-bgp)# redistribute static
device(config-bgp)# exit
device(config)# interface ethernet 0/1
device(config-if-e10000-0/1)# ip address 10.33.36.2/24
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. EBGP is configured between VPN1 and CE 1. 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 signaled LSP named "tunnel1" to PE 4.

device(config)# interface loopback 1
device(config-lbif-1)# ip address 10.2.2.1/32 
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-vpnv4u)# exit

device(config-bgp)# address-family ipv4 unicast vrf VPN1
device(config-bgp-ipv4u-vrf)# neighbor 10.33.33.2 remote-as 2
device(config-bgp-ipv4u-vrf)# 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-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 10.33.33.3/24

PE 4 configuration

This configuration example describes what is required to operate the PE 2 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. EBGP is configured between VPN1 and CE 5. IBGP with extended community attributes is configured between PE 4 and PE 1.

The OSPF area is specified as 0 and MPLS is set up for OSPF traffic engineering. In addition, MPLS is configured with a signaled LSP named "tunnel1" to PE 1.

device(config)# interface loopback 1
device(config-lbif-1)# ip address 10.2.2.2/32 
device(config-lbif-1)# ip ospf area 0
device(config-lbif-1)# exit

device(config)# vrf VPN1
device(config-vrf-vpn1)# rd 1:2
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)# neighbor 10.33.36.2 remote-as 2
device(config-bgp-ipv4u-vrf)# 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 10.33.35.1/24
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 10.2.2.1
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)# exit