[Bob Denny]

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.

[Bob Denny]

I should mention that the one-way audio affects only the iPad softphone, and it affects calls to and from the PBX. ALl other extensions work, and calls to the outside wre working. In other words the audio from the PBX to the 3CX softphone on the iPad via the topology I described above is failing.

[SY]

Please provide debug level (server) log of the call where you have one way audio. Very probable, it can be solved...

[eagle2]

What make is your router ?
Have you tried with NAT helper off ?

Regards

[Bob Denny]

I will get the log and try with NAT helper off. Need to get back to where my iPad is!

[eagle2]

This looks like a typical NAT / firewall issue (nothing so surprising, really). In some cases NAT helpers are not useful.
Wireshark capture may be useful too.

Regards

[Bob Denny]

Orlin --

This looks like a typical NAT / firewall issue (nothing so surprising, really).

Yes, typical, and no, not surprising. Extremely irritating also. This is a ridiculous internet standard. I'll be happy when they get the tunnel into the iPad phone. Well, happier anyway :-)

NAT Helper OFF does not help at all. What does it do anyway???
Router very common Linksys WRT-54G.

Cannot get debug log for a day or two.

[eagle2]

I agree, it is irritating. On the other hand it could be something very stupid like STUN is not working, etc. (may be not configured properly). It is difficult to guess without some debugging. I myself prefer wireshark capturing, nevertheless you need some experience and understanding of networking technologies to do it. However focus your efforts in this direction (NAT/firewall), may be you can have somebody on site to help you.

Try also another router if possible (no reason for not working with WRT-54G, but I would recommend something like NetGear WGR614v9 -- it is working fine with VoIP, and of course other brands/models). There is a problem with Linksys and most SOHO routers, if you try to use 2 SIP devices behind it (registered to external SIP server, e.g. 3CX system) -- at least there wouldn't be any voice between them. Your case may be similar.

Regards

[SY]

The problem is that almost all routers which are trying to "help" to SIP protocol are supporting only one SIP agent in the local network. As the result, when you try to connect more then one phone it immediately highlights all the problems related to the router functionality. It is reality, even if it is irritating. Routers which are not trying to provide "bear" help are working reliable.
Another aspect of the problem is implementation of NAT. Many implementations are falling down to complicated (and buggy) workarounds in case if more then one local agent is using the same "local" port to communicate with the same external IP:port. It is also very irritating...

Tunnel was created just because we know about these problems.

[leejor]

If you use other devices, behind the same router (remote?) as the iPad, did you give each a unique port number?

[Bob Denny]

OK, thanks to everyone who gave me some hints. I have some ideas and will try Monday. Thanks again!!