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External Extension

Discussion in '3CX Phone System - General' started by voip-ch, May 28, 2009.

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  1. voip-ch

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    Hi there

    Ich habe a small problem here. We have a 3CX PBX installed connected with various SNOM 300, SNOM820 and Siemens IP Phones, connected via Patton 4552 to ISDN lines. Everything works perfectly and smoothly with all LAN based phones. We wanted to add a SNOM300 as external extension outside Firewall connected to PBX but hav now faced following issue.

    The external SNOM300 connects and register without any problems to the PBX. I've watched the VOIP Video Nuggets to ensure we have the right settings. This external extension can now call without any problems any internal and external numbers and audio just works fine.

    Problem:
    Every extensions located behind the firewall on the LAN can call the SNOM300 and it does ring but at the end no connection is being made and the call is being diverted to the VM while the SNOM300 on the external net continues to ring.

    Firewall:
    Firewall is according firewall checking tool well configured and without any port translation. FW is a Cisco with Full Cone, one to one NAT. Ports 5060, 9000-90049, 5090 are open accordingly. 3CX STUN has been added to the SNOM300 and enabled in 3CX PBX.

    Has anyone any idea?
    Many thanks
    Chris

    08:32:17.018 [CM503008]: Call(1): Call is terminated

    08:32:05.987 [CM503007]: Call(1): Device joined: sip:999@127.0.0.1:40600;rinstance=da84f29f1893f4ba

    08:32:05.987 [CM503007]: Call(1): Device joined: sip:108@192.168.1.xx:1025;line=p9b3o201

    08:32:05.972 [CM505001]: Ext.999: Device info: Device Identified: [Man: 3CX Ltd.;Mod: Voice Mail Menu;Rev: General] Capabilities:[reinvite, replaces, able-no-sdp, recvonly] UserAgent: [3CX Voice Mail Menu] Transport: [sip:127.0.0.1:5060]

    08:32:05.972 [CM503002]: Call(1): Alerting sip:999@127.0.0.1:40600;rinstance=da84f29f1893f4ba

    08:32:05.472 [CM503005]: Call(1): Forwarding: Ext:Ext.999@[Dev:sip:999@127.0.0.1:40600;rinstance=da84f29f1893f4ba]

    08:32:04.222 [CM504002]: Ext.100: a contact is unregistered. Contact(s): [sip:100@192.168.1.xx:1024;line=5vr6s9jj/100]

    08:31:55.160 [CM503004]: Call(1): Calling: Ext:Ext.200@[Dev:sip:200@x.x.x.x:2053;line=jxz5ewvg]

    08:31:55.160 [CM503010]: Making route(s) to <sip:200@192.168.1.50;user=phone>

    08:31:55.144 [CM505001]: Ext.108: Device info: Device Identified: [Man: Snom;Mod: 8xx series;Rev: General] Capabilities:[reinvite, replaces, able-no-sdp, recvonly] UserAgent: [snom820/8.0.12] Transport: [sip:192.168.1.x:5060]
    08:31:55.144 [CM503001]: Call(1): Incoming call from Ext.108 to <sip:200@192.168.1.x;user=phone>
     
  2. SY

    SY Well-Known Member
    3CX Support

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    May be, it will be slightly "fuzzy" description but...

    SIP/RTP environment has following rule:
    each entity specifies its own location for other party.
    Except some specific cases, it means that:
    1. if entity doesn't receive SIP requests (signaling part of the call) then it most probably the location specified by this entity is not reachable.
    2. If entity doesn't receive audio (but signaling is ok) then it most probably the SDP delivered to other party doesn't contain correct connection information

    In your case:
    Phone is not reachable for PBX, so problem is on the phone side(network), not on the side of PBX.

    I hope my information will help you to find the source of problem.

    Thanks :)
     
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  3. discovery1

    discovery1 Member

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    What sort of firewall is the Snom at the remote site sitting behind?
    Check that it is not modifying the packets or blocking the incoming RTP stream - some firewalls that aren't SIP aware can cause this issue.
     
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  4. voip-ch

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    thanks for your advice. So here is the challenging part. I've placed the SNOM300 at remote site even live on the web, so behind no firewall at all directly connected with a public IP.
    What I've found out so far is that is seems that it must be a SNOM Problem as I've tried to use a 3CX VOIP Client at remote site and, though it was a very quick test, it seemed to work. Any idea what setting could cause something like that on the SNOM Phone?
    Christian
     
  5. SY

    SY Well-Known Member
    3CX Support

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    Christian,
    There is no any type of "challenge" :)
    you can find some information here wiki.3cx.com
    you can find some information here wiki.snom.com
    you can find some information here http://www.3cx.com/blog/voip-howto/snom-370-remote-extension-plug-and-play/
    You can also search for information provided by manufacturer of your NAT/firewall device.

    Thanks
     
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