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3cx behing Microsoft TMG...issue with one way outgoing sound

Discussion in '3CX Phone System - General' started by Thona, Aug 15, 2010.

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  1. Thona

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    Hello,

    I am running a 3cx server behing a Microsoft TMG 2010 (Threat Management Gateway, successor of ISA Server).

    TMG added support for SIP includign a full gateway. At one point in the past it was working, installing TMG Sp1 did seem to break something.

    Works mostly fine - except OUTGOING calls ;)

    * When I take an incoming call, both audio directions work perfectly.
    * When I make an OUTGOING call, the audio line FROM the external system to my internal phone does not work (stays quiet).

    Anyone an idea how to fix this? The system is rarely used (mostly when I travel, rarely outgoing) and this went unnoticed for some weeks. I recently upgraded to 3cx 9, TMG 2010... and now have the problem that I can not do outgoing calls ;) Which interesting is the main reason to use the pbx (when I travel - using a mobile phone in a foreign country is EXPENSIVE).

    Any guideline for how to fix that? How to set up TMG?

    Regards
     
  2. berlic

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    Aug 24, 2010
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    Hey!

    I had the very same issue: http://forums.isaserver.org/TMG_SP1_breaks_VoIP_functions!_%5bsolved%5d/m_2002103091/tm.htm

    The thing is - TMG is agressively modifying SDP/RTP packets to "help" you implement VoIP behing it.
    I hate this! And it seems it can't be turned off.

    To please TMG, you need to convince asterisk that it is NOT using NAT.
    To do this, you need to turn off nat in general and in every SIP-trunk setup.
    In TMG use VoIP wizard to setup "phones directly connect to external IP-PBX" and phones' IP is your asterisk's IP.

    Hope, this will help.
     
  3. MojoDK

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    Sep 22, 2010
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    Re: 3cx behing Microsoft TMG...issue with one way outgoing s

    It might sound stupid, but I'm a noob on this. Where and how do you turn off nat in 3cx?

    I have TMG 2010 SP1 and when users dails in, they hear no audio at all.

    I'm all lost here and we've been down a couple of days now :(

    Thanks!
    Mojo
     
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