A Distributed Denial of Service ( DDoS ) attack is usually instigated on a primary server that provides important services in a network. However such DDoS attacks can be identified and mitigated by the controller in a Software Defined Network (SDN). If the intruder further performs an attack on the controller along with the server, the attack becomes successful.In this paper, we show how such a combined DDoS attack can be instigated on a controller as well as a primary server. The DDoS attack on the primary server is instigated by compromising few hosts to send packets with spoofed IP addresses and the attack on the controller is instigated by compromising few switches to send flow table requests repeatedly to the controller. With the help of an emulator called mininet, we show the severity of this attack on the performance of the network. We further propose a common technique that can be used to mitigate this kind of attack by observing the variation of destination IP addresses and setting different priorities to switches and handling the flow table requests accordingly by the controller.