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SIP voice call issue "no audio"

Fabio Ermotti

Hello,

we have 3CX PBX server on internal network and enabled VoIP (Network Protection-->VoIP-->SIP) on our UTM v9 (9.409-9) to allow SIP comunication with our VoIP provider: all seem works fine but sometimes a phone call is established without audio or a call is broken unexpectly. We don't have intrusion prevention enabled on phone networks interface and UTM logs don't show dropped or rejected packet.

Could you confirm that SIP ALG is under Web Protection-->Application Control? We have Network Visibility disabled.

Any help will be welcome to investigate the problems, thanks.

Kind regards,

Fabio



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  • 0

    Hi Fabio,

    SIP can be blocked via Application control as we have a signature under Web > App Control. If you do not capture any drop logs anywhere I suspect that the disconnection occurs from the UTM side. When a call get's disconnected did you check the WAN link usage in logging and reporting> Network usage; is it fully utilized. Also check that Anti-DoS is not configured.

    Thanks

    Sachin Gurung
    Team Lead | Sophos Technical Support
    Knowledge Base  |  @SophosSupport  |  Video tutorials
    Remember to like a post.  If a post (on a question thread) solves your question use the 'This helped me' link.

  • 0 in reply to sachingurung

    Hi Sachin,

    our Application control section is Disabled and IPS is not active on SIP network interface. The problem that happens more often is the call without audio: checking the SIP log session all seems OK but we need to investigate if there is some particular reason for the firewall to rejected or drop audio packet after SIP session is active.

    Thanks a lot for the moment!

    Fabio

  • 0 in reply to Fabio Ermotti

    Hi Fabio,

    If it is an intermittent issue, I doubt it has anything to do with the UTM. As UTM will not permute the communication dynamically. Again, when you disable Intrusion Prevention, you only disabled Snort - you do not disable the items on the other tabs. For example, many people are tripped up by the UDP Flood Protection which is logged in the Intrusion Prevention log file. This is often the cause of bad voice-quality with VoIP on the UTM.

    Thanks

    Sachin Gurung
    Team Lead | Sophos Technical Support
    Knowledge Base  |  @SophosSupport  |  Video tutorials
    Remember to like a post.  If a post (on a question thread) solves your question use the 'This helped me' link.

  • 0 in reply to Fabio Ermotti

    Hi, Fabio, and welcome to the UTM Community!

    Please read #1 in Rulz.

    Cheers - Bob

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
  • 0 in reply to sachingurung

    Hi Sachin,

    Thanks for the suggest. I have checked IPS log but I didn't found anything about dropped packet related to SIP communication. Also we don't have any of Anti-DoS/Flooding option active.

    We will continue to investigate.

    Fabio

  • 0 in reply to BAlfson

    Hello Bob,

    Thanks for the suggest, we have already read it.

    Fabio

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