A method and system for augmenting routing decisions in a network switching device with topology information acquired using source learning are disclosed. In the preferred embodiment, the method of selecting a port to transmit an outbound flow from a first node to a second node comprises the steps of identifying a plurality of ports associated with minimal equal-cost paths from the first node to the second node, and if an inbound flow from the second node is detected on a first port of the plurality of ports of the first node, then transmitting the outbound flow from the first port. In the absence of an inbound flow from the second node, the first node generally selects the port for the outbound flow from the plurality of minimal equal-cost paths. The present invention allows a switching device to take advantage of the path determination made at another router in the network while avoiding inconsistencies between conventional route selection operations and IP source learning in switching devices adapted to perform bridging on IP address.