I am using freepbx. I installed it successfully and able to registered extension. i created SIP trunk with my Cisco call manager and able to dial calls outside. I natted my freepbx with public IP and also open the ports on my firewall even i open all ports for testing. My network structure is like, on the top layer my ISP router is place, ISP router connected with my Firewall and after firewall i connected my PBX. some access list is configure on ISP router and i already open all the ports for my natted freepbx ip. I also define real IP and local IP in freepbx and also put extension as nat. From outside of the network over internet i am able to connect my extension through x-lite and also able to make calls. The main problem that i am facing right now is one way voice. The called party is able to listen my voice but i am not able to listen any thing. Please help me out in this.