In this paper, an efficient tool has been designed and implemented to design and analyze the communication networks. A network simulator in software is valuable for network managers to design, develop, test and diagnose network protocols and predict operations of designed networks without any hardware consumption. Unlike other commercial ones, a user can easily design networks with simple setting up procedures and intuitive interfaces in our system in which user friend approach has been introduced. The generated traffic reflecting a user's requirement level is flowed in the designed network and its performance is analyzed. Simulation processes are based on the actual behaviors of network devices and protocols. We have presented a practical use for the implementation of network design and analysis tools limited in the areas of partial and theoretical researches. Key Words Network Design, Analysis, Simulation, Traffic Modeling