hi irfan, i install h.323 gatekeepers as you say and then add the server which isa installed on it as the gatekeeper server then open the properties of this server and in network tab i select the internal network card of isa server and also in h.323 application filter i select the check box of allow audio and video and allow t120 and use dns checkbox and check the "use this gatekeeper checkbox" and browse to the isa server is there something wrong or missing to do because still realplayer cann't connect to internet also if there some steps missing to do at real on user workstation thank u very much for helping me