the last few years, VANET has become an active area of research. Vehicle on road like car, busses, van etc. perform the role of node in VANET that moved in unbounded area and in any direction with varying speed. These nodes makes traffic in VANET and have high dynamic nature from which communication path is disconnected frequently in between source and destination nodes. The process of disconnection and reconnect node through new path decrease the performance of network, for example low throughput, high delay and high overhead. This all are also poses new challenges to researchers for reconstructing the protocol for VANET. Recent research work in VANET emphasis on particular areas like routing, security and quality of service but still there are scope for reconstruction or creation of new design of protocol, services for VANET architectures. This paper presents the current exhaustive investigation of numerous routing protocols and ongoing research in VANET with their merits & shortcomings, which can be used for further enhancement of existing protocol or development of new efficient and more reliable protocols for most of the applications in VANET.