3CX Phone 1.1.4 on iPad, iOS5. Registers fine, can call out and can receive calls. 3CX V10 switch on public subnet here, of course has public IP. iPad on WiFI behind a NAT/wireless router whose public IP is also on our public subnet. How simple is that? 3CX/iPad 192.168.1.nnn (DHCP) <-> Router 70.167.x.y <-> 70.167.x.x 3CX Switch On the iPad, both local and external PBX IP are set to the switch's public IP 70.167.x.y. NAT Helper (??) is ON, STUN server is stun3.3cx.com/5060, the default. For the user of the iPad, both incoming and outgoing calls have no remote party audio. In both cases the remote party can hear the iPad user. Calls complete just fine in both directions.