You need to use the corresponding function (fix_nated_sdp) from nathelper module. This function is not available in mediaproxy module. See the mail archives, there are several configuration examples posted. This would work if your call to the Cisco gateway. Receiving calls from the Cisco would not help in this scenario, you need to use a rtp proxy for this either flavour your chose. Adrian Thanks Jan, i am trying without use_media_proxy() but when SEMS answer the call, try to send RTP of greeting to the ip/port of the received SDP invite message. If i dont use media_proxy the c= line of the SDP received by sems is a private ip address. For this reason SEMS receive an icmp error message, cannot reach the private address. Also if the caller is a Cisco gateway with a public IP address, sems start sending the RTP of greeting to the public ip/port of the gateway, but receive an icmp port unrecheable message. (the Cisco gateway dont send a=direction in your SDP body). You explain about the SDP a=direction:active. This must be set in the SDP of the INVITE or in the SDP of the 200OK sent back by sems ? If i am using mediaproxy and not nathelper, can i set the a=direction:active in the SDP contents ??? -- Adrian Georgescu Founder ag-projects.com