A method for using Patricia tree and longest prefix match for policy-based route look-up is described. Five route classes are determined based on a source address, a source address length, a destination address, a destination address length, and an ingress interface. Route classes are prioritized based on their content. A prefix for the first two route classes includes source and destination information. A prefix for the third and fourth route classes includes source information only. A prefix for the fifth route class includes destination information only. Four different route keys are constructed based on the route classes. The route keys are stored in a Patricia tree structure. For routing a data packet, a longest prefix match look-up is performed for a route key in descending priority order for the route classes.