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incoming and outgoing calls failing sometimes RRS feed

  • Question

  • Hello everybody,

    some of our colleagues have problems with external/internal calls. When the colleagues try to call a person, sometimes the message "connection is established" appears and nothing happens after that. The problem occurs very sporadically and currently only affects 3-5 colleagues. It also makes no difference whether the colleagues are in the internal or external network.We could not find any difference  in the configuration between the colleagues where it works and those where it does not work.

    In the local skype logs you will find the following error:

    ms-diagnostics: 10503;source="x";reason="Gateway responded with 503 Service Unavailable";component="MediationServer";SipResponseCode="503";SipResponseText="Service Unavailable";sip-reason="Q.850 ;cause=42";GatewayFqdn="x;trunk=x"
    ms-diagnostics-public: 10503;reason="Gateway responded with 503 Service Unavailable";component="MediationServer";SipResponseCode="503";SipResponseText="Service Unavailable";sip-reason="Q.850 ;cause=42"
    Reason: Q.850 ;cause=42


    • Edited by askque Thursday, February 27, 2020 2:18 PM
    Thursday, February 27, 2020 1:38 PM

All replies

  • Hi askque,

    What do you do before this issue appearing?

    This response from a gateway can occur if the gateway or intermediate PSTN entity is not in a state that can process the request.

    Here are some tips to help you troubleshoot what might cause this issue:

    1. Reboot the server and try again.

    2. Check for unexpected maintenance.

    3. Server connectivity issues.

    4. Make sure the firewall configuration is no problem.

    5. Check if there is any related error message in the Lync server event log.

    For more details about these tips, you can refer to this blog: https://airbrake.io/blog/http-errors/503-service-unavailable.

    Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link.


    Best Regards,
    Sharon Zhao


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Friday, February 28, 2020 5:33 AM
  • Hi askque,

    Is there any update on this case?

    Please feel free to drop us a note if there is any update.

    Have a nice day!


    Best Regards,
    Sharon Zhao


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Tuesday, March 3, 2020 9:09 AM
  • There are no news yet. I'm just about to test it.
    Tuesday, March 10, 2020 12:39 PM
  • i have tried the above mentioned things and unfortunately had no success.

    I could find the following information on the server:

    Reported by Server

    10503; source=xx"; reason="Gateway responded with 503 Service Unavailable"; component="MediationServer"; SipResponseCode="503"; SipResponseText="Service Unavailable"; sip-reason="Q.850 ; cause=38"; GatewayFqdn="IP-Adress; trunk=IP-Adress

    Reported by Client

    12006; reason="Trying next hop"; source="xx"; PhoneUsage="xx"; PhoneRoute="xx"; Gateway="xx"; appName="OutboundRouting"

    In the Lync Logs you can find the following errors:

    An attempt to route to a gateway failed.

    Could not route to Gateway x, the attempt failed with response code: Timeout (CallID: x).
    Failure occurrences: 195, since 1x 16:05:19.
    Cause: A gateway failed to respond to a request within allotted time or was unable to route the request due to some error.
    Resolution:
    Check whether the specified gateway is up and is properly configured.

    A call to a PSTN number failed due to non availability of gateways.

    Called Number: +x
    Phone Usage: x
    Route: x
    CallId: x

    Cause: All gateways available for this call are marked as down.
    Resolution:
    Verify that these gateways are up and can respond to calls.

    • Edited by askque Thursday, March 12, 2020 2:28 PM
    Thursday, March 12, 2020 1:36 PM
  • Hi askque,

    According to the error message, it could be the issue of the wrong configuration from either Lync server side or the Media Gateway side.

    On Lync Server side, you can test the outgoing PSTN number by Lync Server Control Panel--Voice Routing--Test Voice Routing.

    On Media Gateway, double check if there is any wrong configuration for the inbound route and outbound route.

    Also try to restart Media Gateway.


    Best Regards,
    Sharon Zhao


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Monday, March 16, 2020 7:38 AM
  • Hello,

    i have done the voice routing test and everything works fine. 

    On the Media Gateway, the configuration also looks right so far

    If it were a configuration problem, it would occur always and not only sporadically right?

    We use as gateway the audiocode1000, are there any known problems with the skype for business 2015 server?

    Wednesday, March 25, 2020 3:16 PM