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Solved No Voice for Extension to Extension calls within the same LAN; hosted 15.5

Discussion in '3CX Phone System - General' started by Johnbenj, Aug 5, 2017.

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  1. Johnbenj

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    Situation:

    3CX 15.5 hosted on AWS; 5 Yealink T42S phones successfully provisioned and deployed on customer's LAN. Inbound and Outbound phone calls all work very well.

    Our problem is that when internal extension call another extension there is no voice head. For example. Extension 111 calls extension 112 and when answered there is no sound. Both extensions show BLF, show the other extension as busy, etc. just no sound.

    As a test I took an extension to my office so it is on a 100% completely different Lan and Wan connection. No problems at all with extension to extension voice calls. Repeated same test with softphones with 100% success.

    Since signalling b/t phone works but there is not sound i am guessing that RTP ports are being blocked somewhere and i would appreciate any guidance on what to look at. Is it a port? is it a codec?

    Thank you in advance. please let me know if more information would be helpful.
     
  2. leejor

    leejor Well-Known Member

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    Have you checked the 3CX activity log to see if there is anything out of the ordinary when compared to an outside call, which you say is working? Have you tried enabling the "PBX delivers audio" option on a few extensions, then tested again.

    When calling set to set, on the same LAN there usually isn't anything to block ports as the sets should be communicating directly with each other, and rarely passing through a firewall or router. It might be a Codec issue, and the Log should show that. If you enable PBX delivers audio, and it works, look for transcoding in the logs, it means that the PBX is converting from one Codec to another. Most users don't restrict the Codecs on purpose, but it could happen.

    Because you didn't state otherwise, I'm assuming that everything is on the same LAN.
     
    #2 leejor, Aug 6, 2017
    Last edited: Aug 6, 2017
  3. neville

    neville New Member

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    Are using stun or sbc?
     
  4. Johnbenj

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    We are using stun.
     
  5. Johnbenj

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    Thank you. I have received some specific instructions from 3CX support indicating the need to have 1:1 NAT for SIP and RTP ports per device. I'll be working on making those changes tomorrow and testing and will update this thread when I have more specific information. I appreciate your response.

    Thank you, John
     
  6. neville

    neville New Member

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    If you have more than a couple of phones, you might want to try the SBC instead of STUN.

    Chuck
     
  7. StefanW

    StefanW Head of Customer Support and Training
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    what will happen if you have more then one IP phone behind one nat base is called herpinn connections and firewalls normally dont like this.

    Basic flow will be - internal phone send traffic to the wan IP of the firewall with destination internal again. As this is not the shortest path normal firewalls block this traffic...

    In this case you should enabled "pbx delivers audio" in all extensions behind the same nat base so send the data to the pbx and back to the other device. Check this academy out, in slide 10 comes this part in the video: https://www.3cx.com/3cxacademy/videos/intermediate/configuring-remote-extensions/

    best here (depending how many internal phones you have) is to use the 3CX SBC (free). In this case the traffic of internal calls will not even leave your network saving wan bandwidth. In this case it should be avoided to enabled "pbx delivers audio".
     
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  8. Johnbenj

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    Is 6 extensions too many to operate without an SBC? We have 6 extensions at one location "remote" to the PBX hosted in AWS. If we do install SBC I want to verify my assumption that it is required at the location where the phones are and not where the PBX is. There is a Windows 2012 server which could be an installation point for the SBC. Is there a reason why that OS wouldn't be supported?

    Also, a quick update: first test indicate that setting "PBX Delivers Audio" at each of the extensions might have solves the interoffice voice issues but i am haven't had 100% confirmation yet.
     
  9. leejor

    leejor Well-Known Member

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    Sorry, missed that fact that the server and sets were not on the same LAN. Some routers may be able to cope with the voice ports, and six sets on the same LAN, however each set will have to have a unique local port number. For less chance of problems it is best to use the SBC. Using the PBX delivers audio option also increases you traffic, if that is a concern, as all conversations route back through the PBX, even from one desk to the other in the same office.
     
  10. Johnbenj

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    update: we found that setting "pbx delivers audio" for each extension solved the problem with intra-office extension to extension voice. Luckily with the small amount of extensions and the really infrequent times that this scenario will be needed I think this will be an ok solution. We have not had to give the phones unique port assignments for SIP or RTP, etc. We are going to start testing the SBC too as we'll need it in the future for sure. Thanks to all that replied with their suggestions and help. Please let me know if there is any more information I can provide. I consider this "solved"
     
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