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3CX V.10 NAT issues: unable to answer call being behind NAT

Discussion in '3CX Phone System - General' started by maxim, Jan 24, 2012.

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  1. maxim

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    Hello,

    I have a problem with a 3CX setup.
    - 3CX sits behind static NAT, a dedicated private IP mapped to 3CX server private IP.
    Most of remote clients (3CX softphone) work ok.
    - Some remote clients that are behind very nasty NAT (external UDP port doesn't match UDP port of softphone client). These clients don't work correctly. My understanding that this is because in SIP packets from these clients port number in 'via' or 'contact' header doesn't match the translation opened on the router.

    Can this be resolved on 3CX server side? Can I force 3CX to send replies (INVITES) to such clients to the ports where packets actually arrived from but not to the ports announced in 'via', 'contact' headers?

    I expect the same problem with RTP path in case call's been established, so the same question regarding RTP: Can 3CX ignore m= attribute of SDP and send media to the port forward media stream comes from.

    Thanks,
    Max.
     
  2. SY

    SY Well-Known Member
    3CX Support

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    Re: 3CX V.10 NAT issues: unable to answer call being behind

    3CX Phone System does not use information, which is specified in SIP/SDP headers by client, blindly.
    Some NAT and/or ISP don't want (or cannot) support VoIP over SIP/RTP. In this case you need to use tunnel (SIP/RTP proxy manager)
     
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