Abstract: Mobile Ad hoc Network (MANET) can be known as an assortment of wireless mobile devices like (Laptops, wireless phones, Personal Digital Assistants (PDAs), devices, printers, etc.) are combined by wireless link with feature Bluetooth and/or IEEE 802.11 (WiFi). In this study, the scalability issue considers the main problem. This issue is evaluated over different network areas sizes and different node’s speeds, circular configurations for the network and one type of traffic FTP. The evaluation was done through the simulation experiments using OPNET 14.5 simulator depending on the throughput, routing overhead and delay.