Configure PEs as BGP Neighbors
BGP is the preferred protocol to transport VPN routes because of its multiprotocol capability and its scalability. Its ability to exchange information between indirectly connected routers supports keeping VPN routing information out of the Provider (P) routers. The P routers carry information as an optional BGP attribute. Additional attributes are transparently forwarded by any P router. The MPLS-VPN forwarding model does not require the P routers to make routing decisions based on VPN addresses: They forward packets based on the label value attached to the packet. The P routers do not require a VPN configuration in order to carry this information.
PE1
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#configure terminal |
Enter the configure terminal |
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(config)#router bgp 100 |
Enter the Router BGP mode, ASN: 100 |
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(config-router)#bgp router-id 2.2.2.2 |
Router identifier for BGP |
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(config-router)#exit |
Exit router BGP mode |
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(config)#router ldp |
Enter the Router LDP mode |
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(config-router)#exit |
Exit the Router LDP mode |
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(config)#router bgp 100 |
Enter the Router BGP mode, ASN: 100 |
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(config-router)#neighbor 3.3.3.3 remote-as 100 |
Configuring ABR1 as iBGP neighbor using it's loopback IP |
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(config-router)#neighbor 3.3.3.3 update-source 2.2.2.2 |
Source of routing updates |
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(config-router)#address-family vpnv4 unicast |
Configure VPNv4 address family |
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(config-router-af)#neighbor 3.3.3.3 activate |
Activate the VPN neighbor |
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(config-router-af)exit-address-family |
Exit address family mode |
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(config-router)#address-family ipv4 unicast |
Configure IPv4 address family |
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(config-router-af)#neighbor 3.3.3.3 activate |
Activate the IPv4 neighbor |
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(config-router-af)#commit |
Commit the transaction. |
PE2
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#configure terminal |
Enter the configure terminal |
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(config)#router bgp 100 |
Enter the Router BGP mode, ASN: 100 |
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(config-router)#bgp router-id 3.3.3.3 |
Router identifier for BGP |
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(config-router)#exit |
Exit router BGP mode |
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(config)#router ldp |
Enter the Router LDP mode |
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(config-router)#exit |
Exit the Router LDP mode |
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(config)#router bgp 100 |
Enter the Router BGP mode, ASN: 100 |
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(config-router)#neighbor 2.2.2.2 remote-as 100 |
Configuring ABR1 as iBGP neighbor using it's loopback IP |
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(config-router)#neighbor 2.2.2.2 update-source 3.3.3.3 |
Source of routing updates |
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(config-router)#address-family vpnv4 unicast |
Configure VPNv4 address family |
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(config-router-af)#neighbor 2.2.2.2 activate |
Activate the VPN neighbor |
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(config-router-af)exit-address-family |
Exit address family mode |
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(config-router)#address-family ipv4 unicast |
Configure IPv4 address family |
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(config-router-af)#neighbor 2.2.2.2 activate |
Activate the IPv4 neighbor |
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(config-router-af)#commit |
Commit the transaction. |
Create VRF
Each PE router in the MPLS-VPN backbone is attached to a site that receives routes from a specific VPN, so the PE router must have the relevant Virtual Routing and Forwarding (VRF
Virtual Routing and Forwarding) configuration for that VPN.
This command creates a VRF RIB (Routing Information Base), assigns a VRF-ID, and switches the command mode to vrf mode. The following example creates a VRF named ComB.
PE1
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#configure terminal |
Enter the configure terminal |
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(config)#ip vrf ComB |
Configure VRF instance |
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(config-vrf)#rd 2:1 |
Configure Router Distinguisher value |
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(config-vrf)#exit |
Exit VRF mode |
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(config)#ip vrf ComA |
Configure VRF instance |
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(config-vrf)#rd 1:2 |
Configure Router Distinguisher value |
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(config-vrf)#exit |
Exit VRF mode |
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(config)#commit |
Commit the transaction. |
PE2
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#configure terminal |
Enter the configure terminal |
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(config)#ip vrf ComB |
Configure VRF instance |
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(config-vrf)#rd 1:2 |
Configure Router Distinguisher value |
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(config-vrf)#exit |
Exit VRF mode |
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(config)#ip vrf ComA |
Configure VRF instance |
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(config-vrf)#rd 2:1 |
Configure Router Distinguisher value |
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(config-vrf)#exit |
Exit VRF mode |
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(config)#commit |
Commit the transaction. |
Associate Interfaces to VRFs
After the VRFs are defined on the PE router, the PE router needs to recognize which interfaces belong to which VRF. The VRF is populated with routes from connected sites. More than one interface can belong to the same VRF.
In the following example, interface xe48 is associated with the VRF named ComB.
PE1
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#configure terminal |
Enter the configure terminal |
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(config)#interface xe49 |
Enter interface mode |
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(config-if)#ip vrf forwarding ComA |
Bind the VRF instance to the interface |
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(config-if)exit |
Exit interface mode |
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(config)#interface xe48 |
Enter interface mode |
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(config-if)#ip vrf forwarding ComB |
Bind the VRF instance to the interface |
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(config-if)#ip address 168.12.0.3/24 |
Assign IPv4 address |
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PE1(config-if)#ip vrf forwarding ComA |
Bind the VRF instance to the interface |
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(config-if)exit |
Exit interface mode |
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(config)#commit |
Commit the transaction. |
PE2
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#configure terminal |
Enter the configure terminal |
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(config)#interface xe48 |
Enter interface mode |
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(config-if)#ip vrf forwarding ComA |
Bind the VRF instance to the interface |
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(config-if)#ip address 192.16.4.2/24 |
Assign IPv4 address |
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(config-if)exit |
Exit interface mode |
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(config)#interface xe49 |
Enter interface mode |
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(config-if)#ip vrf forwarding ComB |
Bind the VRF instance to the interface |
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(config-if)#ip address 168.12.4.2/24 |
Assign IPv4 address |
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(config-if)exit |
Exit interface mode |
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(config)#commit |
Commit the transaction. |