as i already submitted the msg for this problem and didnt get any response to solve it imrepeating it again can any body read it and reply me ???? the problem is very strange. voice communication from internal to external users is not possible. But if external user send invitation by using MSN Messenger so it works (vice versa not) some of PC2phone services are not working. but Net2phone is working. I have configured H.323. I have create new portocol def to open the required ports and add it to protocol rule. I create allow all rule as well. Firewallclient is installed on the machines. can anybody help me 4 this? thanks Khurram Khan System Engineer Alnafitha IT