Airplay not working on iPad with WiFi network

My iPad has fully been updated with the OS 4.2 and I also have updated my new AppleTV with the latest updates. After I do all of the required steps to login with my Apple ID, the Apple TV does not detect the iPad. When I play a video on the iPad, there isn't a airplay logo appearing in the control bar. The Airplay is not working.The problem seems to be caused by the router. Make sure all of your