The integration of WiFi and WiMAX will allow a seamless connection between users for both connections with larger capacity, higher speeds and mobility access. A special router is needed to allow the interconnection between two different protocol network known as WiFi/WiMAX router. In this paper, we investigate and simulated based on the scenario using OPNET modeler simulation tools and compared their throughput, packet dropped, MOS value and jitter. To have an optimized network, we investigate the number of WiFi users or hotspots can could accommodate a WiFi/WiMAX router and a WiMAX Base S tation. In addition, we also evaluated the suitable applications or traffic combinations for all the WiFi users on the network to fully utilize the given bandwidth. This type of integration will solves many of the difficulties in last-mile implementations, which also will benefit both users and service providers.