This paper first describes the characteristics of Mobile Ad hoc Networks (MANETs), and their Routing protocol, and second a mobile ad hoc network (MANET) which consists of set mobile wireless nodes (25, 50, 75, and 100) and one fixed wireless server are design using OPNET Modeler 14.5. The performance of this network under different routing protocol is analyzed by three metrics: delay, network load and throughput. The comparison analysis will carry out about these protocols and in the last the conclusion shows which routing protocol is the best one for mobile ad hoc networks.