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VOIP over VPN has multiple dropouts per second

Hello,

I run a 3cx on premise that has to be accessed through an OpenVPN tunnel on a Sophos UTM9 firewall. Unfortunately, it is only possible throug VPN because the users work on a terminal server (RDP). In there the 3cx web client runs on a web browser.


After a few tests it turned out that everything is OK without VPN. When the tunnel is on, there are many short dropouts per second. If you concentrate you can barely understand what the other person said.


Do you have any idea what may be the issue?


Here are some more details:


- internet connection with 350 MBit Up / Down (measured)

- Sophos UTM 9 with

      - Bandwidth prioritization each 5000 Kbit/s for PBX / RDP / VOIP

      - OpenVPN

      - deactivated content filter / IPS


It was tested on client side with 2 Fritzbox routers with each 50/10 Mbits Down/UP and 60/12 Mbit Down/Up with the exactly same result.



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  • Hello Martin,

    have a look at Bob's "Rulz" #1   here: https://community.sophos.com/utm-firewall/f/recommended-reads/22065/rulz

    If that doesn't reveal anything useful,

    As a wild guess: I would completely disable bandwith priorization / QOS / application control, then test again.

    Mit freundlichem Gruß, best regards from Germany,

    Philipp Rusch

    New Vision GmbH, Germany
    Sophos Silver-Partner

    If a post solves your question please use the 'Verify Answer' button.

  • Hello Martin.

    I would first check "flood protection" in in intrusion prevention as it is still active when you disable the global tab on intrustion prevention.

    You should see some of those errors within the logs.


    Sophos Gold Partner
    4TISO GmbH, Germany
    If a post solves your question click the 'Verify Answer' link.
  • Hallo Martin,

    If you haven't already solved this, please show pictures of the Edits of the relevant bandwidth prioritization configuration.

    Also, I'm not sure I understand the problem you're experiencing.  Is the VoIP traffic traversing the SSL VPN tunnel or does activating the VPN disrupt existing VoIP traffic?

    Cheers - Bob

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
  • Hallo Bob,

    the VOIP traffic was tunneld through the VPN because the user work in a RDP session. But I bypassed the problem by installing the 3CX client on the Laptops, so the user can remote control the client from the terminal session.