Vehicular Ad hoc Network (VANET) has gained a lot of interest in academia and industry domains. High speed of vehicles, rapid change in topology and environmental characteristics of the city make the routing in VANET a very challenging problem. Traditional VANET routing protocols where decisions are made solely on local neighborhood observations have shown poor network performance. In contrast, the use of the Software Defined Network (SDN) paradigm, which is based on the global traffic view, has proven to be efficient in improving such performance. Internet of Vehicles (IoV) has emerged as a new technology that extends VANET architectures such that to meet the ever growing Intelligent Transport Systems (ITS) requirements. This paper surveys both traditional and SDN-based VANET routing schemes with a comparative study involving the main relevant performance parameters. It also gives an investigation of integration of SDN into an IoV environment that has shown to be very beneficial with respect to network performances.