Finally I can make calls with netmeeting from the DMZ to the local LAN and vice versa. The H.323 Gatekeeper is configured, due the help of the articles in the learning zone. Thank you, it's a great site!!! Our first firewall (Linux FW - DMZ - ISA - LAN) is based on Linux. According the info of MS, I have opened the tcp ports 1720, 1739 and all high ports for the secondary connection. The netmeeting connections are build up normally, but only the internet client gets a voice. The LAN client cannot hear the internet client. Does anyone has an idea? Thank you, Manfred