In traditional networking, distributed inter-domain networking is conventionally done through BGP based protocol. As in BGP, the topology information is flooded in the network and route is locally computed which creates high bandwidth, over process utilization, excessive storage occupancy, slow convergence, complex and unsalable networking. To overcome network issues, some means of network control centralization are anticipated which emerge Software Defined Networking (SDN) in which network core is fragmented into Control plane and Data plane. Different application and services are boarded on the control plane and data plane act only as a forwarding plane. In SDN, routing is also computed on SDN control plane. However there is not a defined and standardized method of routing in SDN and routing is computed on the essence of conventional protocol. In which information is gathered at data plane and forwarded to control plane which define rules and policies of the basis of these information. How to exchange information in a centralized environment in an optimized ways which can benefit network is main issue in SDN. In this paper we have studied different routing strategies of routing and present a brief survey of SDN routing techniques. The survey on SDN routing in not yet done upto our knowledge. In this survey, we have highlighted some very common routing strategies adopted in SDN; throw light on merits and demerits of these techniques. Correspondingly focus on relevant issues of routing in SDN.