With the recent developments of communication technologies surrounding vehicles, we will be witnessing the simultaneous availability of multiple on-board communication interfaces on vehicles. While most of the current interfaces already include Bluetooth, WiFi, and LTE, they will be augmented further by IEEE 802.11p and the 5G interfaces, which will serve for safety, maintenance, and infotainment applications. However, dynamic management of interfaces depending on application needs will become a significant issue that can be best addressed by Software Defined Networking (SDN) technology. While SDN-based vehicular networks have been promoted previously, none of these works dealt with their practical challenges. In this paper, we propose and develop a practical framework that will realize SDN-based vehicular networks for a wide range of applications. Through this framework, we demonstrate a platoon example which demonstrates the use of SDN for quick and efficient multi-hop messaging. The route from source vehicle to destination is computed with the help of the SDN Controller to transmit the Beacon Safety Messages through Road Side Units (RSUs) at the MAC layer without relying on IP for proper platooning operations. The results show the efficiency of the SDN-based approach compared to the traditional routing approaches.