Software defined networking (SDN) is a new architecture for computer networks in which control plane is decoupled from data plane and is implemented centrally. Entrance of SDN in companies requires upgrade of legacy network equipment which will have high costs for the company. The solution to this problem is gradual deployment of SDN in form of hybrid networks. Hybrid networks necessitate communication control plane of traditional switches and the SDN controller. This communication help us to use SDN capability in hybrid networks. The loop problem in layer 2 can be solved in simpler way with using of SDN controller. Also, we can reach better management and load balancing with SDN controller in traditional networks. We studied two problems in this thesis, solve loop problem in layer 2 hybrid network and new indirect way to communicate SDN controller and control plane of legacy devices for managing direction and traffic. We proposed three solution for preventing loop in hybrid network. In first solution, OpenFlow switches support spanning tree protocol like legacy switches. In two other solution we used SDN controller for preventing loop without using spanning tree protocol. At the end we studied a new indirect way for communication of SDN controller and control plane of legacy devices for better managing direction and load balancing. This communication can happen using traditional network management protocols which has limitations and difficulties. In the given procedure in this thesis, it is assumed that the protocol for routing in the network is RIP. The OpenFlow switches send advertise packets with fake metric toward the legacy router. With this procedure we can change the routing table of legacy router based on the controller policies indirectly. Key Words : Software Defined Network, Hybrid Software Defined Network, ARP Protocol, RIP Protocol
