Software Defined Networking (SDN) constitutes a fundamental technological solution which responds to the most essential challenges in 5G and beyond networks. Security still remains one of its most controversial issues. Security should be ensured in order to create reliable and consistent networks and on line applications and satisfy the demands of Service Level Agreements (SLAs). Therefore, teaching security of SDN and NFV is fundamental for academia these days. In this paper, we are going to summarize the most fundamental issues related to SDN security challenges and problems appearing alongside with the key back-doors in future SDN mobile networks. Several solutions utilizing SDN capabilities are suggested to avoid SDN security issues. We are also presenting experiments of network topologies using well-known network attack scenarios performed to showcase how networks' security could be taught using SDN controllers. Experiments are conducted using the Open Network Operating System (ONOS) controller indicating that security teaching using ONOS controller is easy and offers many benefits. Future research activity in the field is proposed.