[Serusers] Redirect to unregistered client behind NAT

[radan]

Hi all !

I have to redirect some calls to unregistered user (private IP) behind NAT
This calls are forwarded to ext_IP:port and NAT redirect calls to this 
user.
I'm not able to register this user on my server or set up external IP for 
him
How can I achieve two way audio stream ?
Do I have to use mangle module or rtpproxy should be enough ?
Default configuation of ser  for rtpproxy works only when this client is 
registered, but I can't  register him. (it doesn't matter why )

When I make a call then only one way audio stream is hearable
(from private to public) becasue public phone want get private address 
unregistered client. How does fix it ??

Thanks
Andrzej