H323 NAT

Well I m making calls from the softsphone which it has the private Ip address but taking the External IP ( I mean it knows what is my public IP , its like mapping ) . This softphone is making a call to the Voice GW AS5350 . I am getting only one way call. The logic I got it is the about the NATTED ports, that are not open in Voice GW. I think I need to open the NATTED ports on GW but how ?? or Can I do it by using GK ???