Fax not working / stops the call

Discussion in '3CX Phone System - General' started by Patrick Müller, Dec 4, 2017.

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  1. Patrick Müller

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    Hi All,
    We are having trouble setting up a fax system with 3cx.
    One of our customers got switched to all ip. (Provider: Telekom, Package: DeutschlandLAN IP Voice/Data S Premium)
    The complete setup is as following:

    Modem: Digitalisierungsbox Smart
    Firewall with PPPoE connection: Watchguard T30, Ports are forwared - Firewall check is fine
    3CX Version: 15.5
    ISDN Gateway: Patton SmartNode 4112
    Fax System: MFP Canon iRC3080i

    The fax number is logged in as a SIP-Trunk to the provider.
    The patton is configured as FXS gateway and provisioned by the 3cx.
    (Local Subnet, Fax Transmission Mode: Fax in Audio G711A(if provider does not support T.38), Fax Extension is added as first Extension)
    Connecting a phone to the gateway works. I can do and receive calls on it.
    When I try to send a fax, it calls the remote station but immediately stops and ends the call when the remote station takes the call.
    We have changed the fax system with no success. We tried to use a software fax (T.38 Printer) without success.
    I'd hope that someone has faced similiar problems and can help me with this.
     
  2. eddv123

    eddv123 Well-Known Member

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    Hi Patrick,

    Firstly you need to confirm your Patton products so there is no confusion.

    You said: "ISDN Gateway: Patton SmartNode 4112".

    The 4112 comes in either FXS or FXO variants not ISDN, confirm you have the correct box for the job. It should be either an SN 4110 (2-8 port) JS (FXS) model as this is the only ones that will do FAX.

    Please also confirm that your provider supports T.38 FAX also as some do not.

    I personally have never had issues with FAX in or outbound with 3CX and the Patton 411x JS range so long as you stick to these guidelines:

    * The Patton must be local to 3CX, in the same subnet and/or locally routed subnet: Issues have arisen before with clients trying to setup a Patton gateway to a hosted 3CX System via SBC and STUN (which is not currently supported).

    * The Patton is auto-provisioned locally without parameter changes or custom template configuration attempts.
    Configuration on 3CX is as per: https://www.3cx.com/docs/manual/fax-server/

    One thing I would check in 3CX under "System extensions" is that the FAX extension you created is registered, from where you have got to I would say it is but please confirm.
     
    YiannisH_3CX likes this.
  3. Patrick Müller

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    Hi eddv123,

    thanks for your reply.

    Patton Model is SN4112/JS/EUI.
    SW: R6.10 2017-09-04 H323 SIP FXS FXO

    The Fax Extension is registerd under "System extensions".

    Update:
    Provider told me that it should be supported. Otherwise we can use G.711 as fallback. This is exactly what we have configured on the fxs.
     
    #3 Patrick Müller, Dec 4, 2017
    Last edited: Dec 4, 2017
  4. eddv123

    eddv123 Well-Known Member

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    Hi Patrick,

    You are running the latest version of firmware as per the website. If you get no luck with your provider you could try running some debug on the Gateway itself.

    Telnet into the Patton using Putty and use the following command string while replicating your issue (be aware there maybe a lot of output depending on traffic):

    enable
    show running-config
    debug call-router
    debug call-control
    debug fxs
    debug ccfxs
    debug context sip-gateway signaling detail 5
    debug context sip-gateway transport detail 5
    debug context sip-gateway error

    After completing the test type in "no debug all" to disable the output.
     
  5. Patrick Müller

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    Hi eddv123,

    you are right, I got a lot of debug information to work through.

    One short question: If the Provider does not Support T.38, should it still work?

    Update: Provider supports T.38. Just received a phone call confirming it.
     
    #5 Patrick Müller, Dec 4, 2017
    Last edited: Dec 4, 2017
  6. eddv123

    eddv123 Well-Known Member

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    #6 eddv123, Dec 4, 2017
    Last edited: Dec 4, 2017
  7. lneblett

    lneblett Well-Known Member

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    Should it still work needs to be changed to might work.

    FoIP is extremely sensitive to the connection stability and the reliability by which the packets are delivered. t.38 was developed to help overcome some of these issue, but is not foolproof. g711 is not nearly as robust as t.38 and therefore even more problematic.

    A packet capture may show some of the issue as there seems to be something going on when you indicated that the remote side answered and then immediately disconnected. This may be related to the Patton trying to Invite to t.38 and it not being supported.

    What happens when you try and receive a fax?
     
  8. Patrick Müller

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    @eddv123: It has been configured for G711 Audio. I followed the guide you mentioned.

    @Ineblett: I tried to receive a fax without success.

    In addition, I tried the new funktion (G711 on fallback) for the fax server which got implemented in 15.5. No success either.

    I'm losing my head in this debug. Is there anything specific I can look for? I don't want to give you 200 lines of debug information to read.

    By the way, thank you for your help.
     
  9. sip.bg

    sip.bg Active Member

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    If your provider is not supporting T.38, there is little chance for successful transmission of faxes.
    G.711 fallback in version 15.5 concerns only fax extensions (ATA), whether they operate in T.38 or G.711 mode, at least from my testing. Most ATAs don't operate reliably in T.38 mode (not the case with Patton), so it is important to have fallback possibility.
     
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  10. eddv123

    eddv123 Well-Known Member

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    Hi Patrick,

    This guide should give you a description of the commands and explanation of each one:
    https://www.patton.com/support/kb_art.asp?art=446&

    Also take note of the command "debug media-gateway fax-data" you may want to try and run this on its own and see if it gives you anything - feel free to post the output for analysis.

    Please also ignore the Trinity commands, as you have a Smartware box.
     
    #10 eddv123, Dec 5, 2017
    Last edited: Dec 5, 2017
  11. Patrick Müller

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    @eddv123:
    Thank you for the link with the description. While I was trying to use "debug media-Gateway fax-data" on its own, I was able to send one fax but got no output on the patton. 2 hours later, when nothing got changed, it failed again and I still can not send or receive a fax.

    @sip.bg: Provider told me that it is supported. Patton is configured to use both. We already changed the priority without success.

    -----------------------------------
    profile voip default
    codec 1 g711alaw64k rx-length 20 tx-length 20
    codec 2 g711ulaw64k rx-length 20 tx-length 20
    codec 3 g729 rx-length 20 tx-length 20
    ced net-side-detection re-negotiation
    fax transmission 1 bypass g711alaw64k rx-length 10 tx-length 10
    fax transmission 2 relay t38-udp
    fax redundancy low-speed 2 high-speed 1
    no fax error-correction
    -----------------------------------
     
  12. YiannisH_3CX

    YiannisH_3CX Support Team
    Staff Member 3CX Support

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    I would recommend testing one thing at a time. Have the Fax number send the Fax to the Fax server of the PBX so you remove the Patton and Fax machine from the equation. Point the DID to Send Fax to and select an extension with an email. Try sending a Fax and see if that works. You should get the Fax as a pdf attachment in the email of the extension you chose.
    If that works then the issue is either with the Patton configuration of the FAx machine. If it doesn't run a wireshark on the PBX server and check it the communication is correct. Also if you are not using a supported provider that supports T38 try getting an account from a supported provider and try with that.
     
  13. Patrick Müller

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    Hi YiannisH_3CX,

    I've tried the fax server. It's not working. Even the new implemented feature with the fallback to G.711 is not working. I use the 3CX SMTP Server. Supportpackages can be send via E-Mail so I guess the mail function is working.

    Do I have to add any Codec to the Sip-Trunk for the use of T.38?

    Looking at the logs, Faxes that have been sent successfully used G.711. I'm more and more thinking that the provider doesn't support it. Even after they told me they do.
     
  14. YiannisH_3CX

    YiannisH_3CX Support Team
    Staff Member 3CX Support

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    Then a wireshark capture on the server is your next step. You should see the invite from the provider hitting the 3CX server and then a re-invite from the 3CX server for T38 (if the destination is the FAX server or a Fax extension). The provider at that point may send a error message or they may not respect the port change for T38. Either way wireshark will tell you whats going on.

    Another thought, is the fax number a separate Trunk on the server or is it defined as a DID on the same trunk? Perhaps the number is not routing correctly? Check how the number is defined in the PBX and how it is arriving from the provider. Perhaps those don't match and your call ends up in a different destination.
     
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