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One-way Audio

Discussion in '3CX Phone System - General' started by mfretwell, Jul 18, 2008.

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  1. mfretwell

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    VOIP: Vonage
    Firewall: SonicWall Pro 2040
    PBX: 3CX 6.0
    IP Phone: Aastra 55i

    Extension is registered, calls ring through and connect both incoming and outgoing, but not getting audio at handset. Can hear audio on external line.

    Any suggestions?
     
  2. Stuck101

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    Did your "firewall tests" pass within your 3CX management console (under General Settings) ?
     
  3. francesco

    francesco New Member

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    you can try with setu up STUN server
     
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  4. mfretwell

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    Firewall tests respond okay.
    Stun server is set to "stunserver.org" port "3478"

    We had the system working fine with one extension under 3CX 5.#
    We started to have problems when we added more extensions to 3CX, but I think that was just coincidental because it was so illogical that it would cause problems.

    Since that time we have upgraded to 3CX 6.0, and the Aastra firmware to 2.2.1.25, but not changed any firewall or basic PBX settings.
    We are gradually working through the problems and are so very close to getting it working, but I must admit it is very frustrating to be so close and not be able to SEE the problem.

    I have tried using Wireshark to monitor activity and try to isolate the problem; we get the following clue:
    270 72.575711000 192.168.0.117 192.168.0.105 ICMP Destination unreachable (Port unreachable)

    This appears to be caused by a checksum error at the UDP layer as per the following message:
    Checksum: 0x8ca6 [incorrect, should be 0xa180 (maybe caused by "UDP checksum offload"?)]

    It's got to be something really simple that we are missing, no?
     
  5. mfretwell

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    I just tried disabling the checksum offload on the server NIC but that had no effect on the error, nor the messages in Wireshark. Still getting a checksum error at the UDP layer...
     
  6. Anonymous

    Anonymous Guest

    Hi there,

    The error you are seeing occurs because the checksum of the header you are seeing in the UDP packet does not match with the payload of the packet itself. This can be cause by:

    1) Faulty drivers for a NIC Card
    2) A device along the route which is modifying the packet in some way (router, firewall, load balancer...) without updating the checksum.

    A network diagram would help.

    Thanks,
     
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