Configuring VRFs

Virtual Routing and Forwarding (VRF) is an IP technology that allows multiple instances of a routing table to coexist on the same router at the same time. Because the routing instances are independent, the same or overlapping IP addresses can be used without conflict. "VRF" is also used to refer to a routing table instance that can exist in one or multiple instances per each VPN on a Provider Edge (PE) router. Scaling limitations of VRFs can be resolved with the implementation of IP VPNs. IP VPNs are most commonly deployed across an MPLS backbone as the inherent labeling of packets in MPLS lends itself to the identification of the customer VRF.

In the network below there is simply one router and four end-user computers. In real world deployments a network could have dozens or hundreds of routers and devices depending on the scale of the network. Regardless of the network complexity VRF provides the same fundamental separation of routing instances. A typical example would be an ISP using same router to route traffic for various customer traffic while using VRFs to separate each customer's traffic from each other. In the below example e will configure VRFs to separate routing instances as needed so that only hosts within each VRF can communicate with each other.