No sounds on internal extensions

Discussion in '3CX Phone System - General' started by Peter Richardson, May 9, 2017.

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  1. Peter Richardson

    Peter Richardson New Member

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    Hi all,

    I am setting up 3CX and need some help.

    Problem: there is no audio when calling from one local extension to another local extension - neither can hear the other. There is no problem when calling a mobile phone or another outside phone.

    1) I am using remote provisioning of phones
    2) I am not using an SBC (I've got this far without it, I can't see the use of it, can anyone enlighten me otherwise?)
    3) I have configured the firewall correctly where the 3CX server lives (offsite) and the firewall test passes.
    4) I am using V15

    under Extensions -> extension -> phone provisioning -> IP Phone, I have selected "direct SIP (STUN - remote)", I have put in the mac address, but the "local sip port of phone" has been auto populated - some of the phones have 5060 and others have 5065.

    Why are some on 5060 and others on 5065? Should they all be 5060? Or should they all have different ports (no two can be alike)?

    Also with the "Local RTP Audio Ports Start/Finish" - they are all set to 14000 - 14009, but in the many firewall/NAT tutorials that I have read, they all say that RTP ports to be opened are 9000 - 9500. Can we get a definitive answer here?
     
  2. leejor

    leejor Well-Known Member

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    I'm assuming that there are a number of extensions (more than 2) all behind a "remote" router. If this is the case, then it is not a recommended set-up for the reason you've discovered. For a couple extensions, perhaps, but for any more, you should be using an SBC.

    The way you are currently set-up, each extension must have a unique local port number. Each set is identified (by 3CX) by the public IP and the port, so duplicate ports will simply cause confusion. Deploying an SBC allows sets to "talk" to each, after call set-up. At the moment, it can't. You will may have some luck with audio by setting each extension to PBX Delivers Audio under Other, as well as changing all of the port number. IT should work, but is not ideal as all audio will go to the PBX and back for set to set calls.
     
  3. Peter Richardson

    Peter Richardson New Member

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    Hi Leejor,

    Thanks for your reply. Okay, I think I understand the benefit of using an SBC now - less leg work between the phones and the PBX - the local traffic can stay local and only the calls to the outside world go via the internet.

    I have set up an SBC on a Raspberry Pi and it is now working perfectly.

    But I'm still not sure about those ports, shouldn't they all be communicating on 5060 and then choose an RTP port between 9000 and 9500?
     
  4. nb

    nb Support Team
    Staff Member 3CX Support

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    leejor refers to the local port on the phone. The remote firewall will get very confused seeing many devices all coming from same source port. Connecting to the same port.Remember that these will all look like PUBLIC IP:5060 if you leave them like this.
    Each local phone needs to have a different local sip port and rtp ranges so you force the firewall to build a dedicated mapping which will be vital for when the traffic needs to be routed back to a particular phone
     
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  5. leejor

    leejor Well-Known Member

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    If you use the SBC then each set can be assigned the same local port (5060) if you want (they can also remain unique port numbers). In this case, each set communicates through the SBC, and each set is seen by the SBC as localIP: port
     
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