Policy Based Routing (PBR) is an advanced packet forwarding feature which is different from conventional destination address based routing. Policy Based Routing (PBR) allows data packets forwarding based on policies defined by network administrators.

In conventional routing, when a packet is received on the router, destination address in the packet is looked upon in the routing table and if the routing entry is found, packet is routed based on routing entry. In policy based routing, routing decision could be made from source address, destination address, transport protocol id, source port, destination port, or a combination of these criteria.

PBR includes a mechanism for selectively applying policies based on an access list or other criteria. Actions taken might include (a) Forwarding a packet to a directly connected ip nexthop (b) Black hole/Drop. If traffic doesn't match the route-map's match criteria, then it will be routed as if no PBR policy exists. PBR config is interface oriented, hence when applied it affects only the traffic ingressing on that interface. It does not apply on traffic egressing on that interface or traffic ingressing on an interface without a pbr route-map.