A network switching device includes a macroflow sub-plane that performs packet-based routing in the network switching device and a microflow routing module that performs flow-based routing in the network switching device. The microflow routing module is separable from the network switching device and operates to provide a data packet via a software defined network agent to an SDN controller. The data packet is associated with a first unknown flow on the network switching device. The microflow routing module further operates to receive via the SDN agent a flow-based routing rule from the SDN controller and route the data packet based upon the flow-based routing rule.