Siemens PBX & Remote SIP Extensions

[OmniTel]

Hi There,

I was wondering if anyone can please assist me in this. I have found multiple posts about the exact reverse of what I am trying to do, but not a single post that addresses my problem.

First some background.

LAN - Network 192.168.1.0/24
WAN - Fixed 196.***.***.***

Siemens HiPath = 192.168.1.22/24

Now, the Siemens PBX has been setup correctly since when I connect the client phone on the LAN it work 100% with the PBX. what I am trying to achieve is that the client phone can register and operate from the WAN side by means of NAT / Port Forwading

I have set PortForward from WAN UDP(5060) forward to 192.168.1.22:5060 and this allows the phone to register when connecting over the WAN. But I have no speech.

The Siemens PBX uses RTP ports 29100 - 29459 by default and I would like to carry on using them. But If I setup another port forwading from WAN TCP/UDP(29100 - 29459) forward to 192.168.1.22:29100 I still get no audio

Has anyone successfully allowed the NAT / Port Forward for a phone client into a LAN network? All other posts is where people have issues with no voice connecting to an external SIP provider. is 1:1 or outbound NAT required in my case?

Any help would be appreciated.