What is policy-based routing (PBR) and when would you use it?

• A. A method to implement fastest path metrics using route maps
• B. Routing decisions based on policies such as source address or protocol; used to override normal routing for specific flows
• C. A firewall feature to block certain traffic
• D. A method to dynamically learn routes from neighbors

Answer: (B)

Policy-based routing uses a configured policy to steer specific traffic along a chosen path, rather than letting the normal destination-based routing table decide every packet. In practice, you define criteria such as source address, destination, protocol, or application, and then specify a different next-hop or exit interface for traffic that matches those criteria. This lets you influence the route for certain flows to meet security, cost, or QoS goals—for example, sending all traffic from a department through a particular firewall or VPN path regardless of what the standard routes would pick. The policy is implemented with route-maps or similar policy statements that match the traffic and set the desired next-hop or interface.

This isn’t about blocking traffic (that’s a firewall function), nor about learning routes from neighbors (that’s dynamic routing), and it isn’t primarily about choosing the fastest path by metrics.