Trouble conecting to AT&T with Border Elements

[ITAdmin]

We are trying to connect our 3CX Server v16.0.1581 to our AT&T Cisco router via SIP. Our AT&T implementation uses the Public Media Address ( port 2 on the Cisco router ) and the Public Signaling Address ( network card on the 3CX server ) along with 2 Border Elements that AT&T has provided. We are currently using the setup with an older in-house PBX, so I know that we can communicate via SIP. However, I am not able to get this to work with 3CX. I can not find a place to specify the Border Elements. 3CX will also not pass the Firewall checker.

My setup is as follows:

1. Ethernet from Port 1 on the AT&T Cisco router ( data ) to a Firewall to network card on the 3CX server. I have verified that I have an internet connection
2. Ethernet from Port 2 on the AT&T Cisco router ( SIP ) to a network card on the 3CX server. I have assigned the Public Signaling Address to this card.

Has anyone ever connected a 3CX server to AT&T using Border Elements? If so, is there a trick to it?

BTW - I have decided to try and setup multiple trunks on the 3CX server. One trunk for the Public Signaling Address and one trunk each for the Border Elements. This is just a shot in the dart but I am not sure what else to try. Any help would be appreciated.

 

[cobaltit]

So how is your old PBX setup? 3CX is a PBX just like whatever you have setup so you'd set it up in similar fashion. And you would make your life easier but having AT&T deliver SIP over the data interface instead of the separate hand-off. Otherwise you need two NICs in your 3CX box.

 

[ITAdmin]

I agree with you about having everything over the same interface, but unfortunately, I can't do that right now. I seem to be stuck with having 2 NICs in my box. I have one setup as my LAN and the other as my Public Signaling Address.

From a trace taken from my old PBX, I can see the Public Signaling Address talking with the Border Element. So, for example, I can see a SIP conversation over port 5060 happening between x.x.1.100 ( Public Signaling Address ) and x.x.x.85 ( AT&T Border Element ). I then can see the RTP conversation occurring between the same 2 IPs, but with a different port range.

I have tried setting up 3CX using my Public Signaling Address as the Registrar/Server/Gateway Hostname with in the Trunk section and using the Border Element as my Outbound Proxy, but that did not work. It was close, because I could get the phone to ring, but there was no audio.

This is an example of a working call from our old PBX to my cell phone

 

[cobaltit]

So there's a couple things you need to do. For your two NICs you should have one connected to the data side and one connected to the VoIP interface. There should be no gateway on the VoIP NIC. You'll need static routes to the box routing the IPBE segments to the Public Media Address (Cisco port).