Call connection / Call Flow

[nivisk]

Architecture
3CX PBX running on remote datacenter
Remote users in Office 1 and Office 2 with the 3CX windows client
Office1 - Extension range 001 -010
Office2 - Extension range 011 - 012
S2S tunnel from between :
Office1<=>Office2
Office1<=>Datacenter
Office2<=>Datacenter

Question

When a call is made from Ext 001 to 011 how does the traffic flow?
Is there any article which I can refer to.

 

[JohnS_3CX]

Hi nivisk

There's no single way the traffic will flow, it will depend on your network setup and whether the client registers on the PBX via its private IP or FQDN.

If you are not sure, you can always run a capture on the PBX and make a call from 001 to 011, then look at the capture in WireShark to see the Flow Sequence from IP to IP. That should give a clear picture.

Is there something in particular you are trying to solve or are you asking for general knowledge?

 

[nivisk]

Hi,
The extensions internally are registered with a private ip and when the users dial from office 2 to office 1 the audio is heard both ways but when retried it is only one way. It goes off and on.
I wanted to calrify whether the dial directly to each other like peer to peer or the audio goes via pbx

 

[JohnS_3CX]

Again this will depend on the option set under the Extension. There is also the options tab under the extension, that define whether PBX delivers audio. If you enable this on all extensions (or if you have recording enabled this is on by default) and guarantees the audio will pass through the PBX and will force the two offices to talk to each other via the PBX.

In addition: To troubleshoot intermittent audio issues however, I would also look at whether the 3CX ports are all open for traffic across the VPN firewalls and also whether SIP-ALG is disabled. Ports are randomized (when tunnel is not in use) so having no audio sometimes might be pointing out to issues with the ports or SIP-ALG interfering.

You should take some captures and make a few calls until you replicate the issue and see the traffic flow if the above suggestions don't help, but it does sound like a network issue.