[Serusers] Problem/Question regarding mediaproxy

Hello, I'm using Ser in combination with Mediaproxy. The situation is as follow: My SER has a private ip address (10.254.254.1), and my UAs also have private IP addresses, they can all see SER, and SER can see the UAs. Next, our company has a Voice Interconnect with a telco. (it's using Cirpack as softswitch). SER can see Cirpack and vice versa. However, the UAs cannot see the Cirpack. So I want to use Mediaproxy to overcome this. I can make outbound calls, but when calling inbound, I sometimes have one-way-voice of no voice at all. I think the problem is related to Cirpack, but I have a question thouh: - When calling mediaproxy, how does mediaproxy decide which one is the caller and which one is the called? Is this based on the From and To header? Because, if i call from PSTN -> SIP, i get serveral thousands (!) of messages saying that the called person signed in (no caller signs in in mediaproxy). This could be due to the fact that the from and to headers are incorrect. My ser.cfg is the one from onsip.org (pstn with nat). I can post configs/traces if someone needs them! Regards, Ronald