I am trying to set up 3 samsung ITP-5121D VOIP phones behind a NAT router. All the phones will connect to the remote system which is a samsung officeserv 100. The system is connected to the internet through a public ip address on a DSL circuit. The problem that I am having is that whenever I try to place a call from more than 1 phone at a time I don't receive any audio. The phones use UDP 6000 and UDP 9000 to communicate with the phone system. How do I configure the router to have all 3 phones use the same ports through NAT.