Required Configuration Sections for IPv4 Layer 3 VPN

BDE.

To enable IPv4 Layer 3 VPN on service provider PE routers, the following three configuration sections are required:

A. Implement MPLS for all customer-facing links: Multiprotocol Label Switching (MPLS) is a technology that enables efficient packet forwarding. It is essential for Layer 3 VPNs as it allows the service provider to create virtual paths between PE routers across its network. MPLS is used to encapsulate customer IP packets with a label that is used to forward the packet across the provider network.

B. Configure route targets that are used for importing and exporting customer VRF routers: A route target (RT) is a BGP extended community attribute that is used to import and export VPN-IPv4 routes between different VRFs. The route target is used to control the distribution of VPN routes across the provider network. Each customer VRF must have a unique route target assigned to it.

F. Configure route distinguishers that are used for importing and exporting customer VRF routes: A route distinguisher (RD) is an identifier that is used to make the VPNv4 address unique. Each customer VRF must have a unique route distinguisher assigned to it.

C. Advertise customer routes to all PE routers by configuring the IPv4 address-family under the MP-BGP configuration mode: To advertise customer routes across the provider network, MP-BGP (Multiprotocol BGP) is used. MP-BGP supports multiple address families, including VPNv4. To enable MP-BGP to advertise customer routes, the IPv4 address-family must be configured.

D. Configure at least one interface that is assigned to a customer link as a member of the VRF: A VRF (Virtual Routing and Forwarding) instance is a separate routing table that is used to segregate customer traffic. Each customer must have a separate VRF. To configure a VRF, at least one interface that is assigned to a customer link must be configured as a member of the VRF.

E. Configure the VPNv4 address-family under the MP-BGP configuration mode on the PE routers that participate in the customer VRF routing: VPNv4 is a BGP address-family that is used to carry VPN routes across the provider network. To enable MP-BGP to advertise and receive VPNv4 routes, the VPNv4 address-family must be configured under the MP-BGP configuration mode on the PE routers that participate in the customer VRF routing.