Vehicular Ad Hoc Networks (VANETs) is an essential and emerging area of research in the field of Ad Hoc Networks. The main objective of deploying VANET is to improve the road safety and reduce the number of accidents. In VANET, routing is a difficult task because of the high mobility of nodes, which causes rapid changes of topology and to deliver a packet within a minimum period of time. Existing routing protocols are not sufficient to meet all the issues in routing. To provide best routing protocol, it is necessary to make an analysis of routing protocols in VANET. This paper starts with the basic architecture of VANET and provides a detailed description of various existing routing techniques with its advantages and disadvantages. Finally, this paper discusses an overview of the existing routing protocols for VANET.