Cisco Policy Based Routing provides a flexible mechanism for network administrators to customize the operation of the routing table and the flow of traffic within their networks. Policy Based Routing (PBR) offers many advanced features, including selection and forwarding of traffic to discreet Virtual Routing and Forwarding (VRF) instances, as well as Enhanced Tracking of the availability of next-hops. More about PBR you can read here.
Before we start this tutorial please download the topology file which contain the routers connection, BGP topology and some explanations. As you can see in the topology file, traffic going from R4 to R5 will choose the shortest path through R1-R2. For this tutorial let’s assume that we want the traffic from R4 to R5 (and viceversa) to flow through path R1-R3-R2 (BGP is full mesh configured among these devices). For this we need to apply Policy Based Routing (PBR) on R1 and R2. What is PBR basically doing? It will change the next-hop for interesting traffic to R3 on this devices.
Please see below the tutorial about how to configure PBR: