FRITZ!Fon MT-F Service - Knowledge Base

FRITZ!Fon MT-F Service

Cannot make outgoing calls over Internet

You cannot use a FRITZ!Fon registered with the FRITZ!Box to make calls over the Internet. One of the following error messages or another message regarding the telephone number may be displayed in the event log of the FRITZ!Box:

  • "Registration of Internet telephone number [number] failed. Reason for error: DNS error"
  • "Registration of Internet telephone number [number] failed. Reason for error: Remote site not responding. Timeout."
  • "Registration of Internet telephone number [number] failed. Remote site reports reason for error: [40x, 50x, 500, 503]"
  • "Internet telephony registration failed [number] Reason for error: [401, 402, 403]"
  • "Internet telephony with [Number] failed. Reason for error: [404, 405, 406, 407, 408, 50x]"
  • "Internet telephony with [number] via [registrar] failed. Reason for error: Not Acceptable Here (488)"
  • "Internet telephony with [number] via [registrar] failed. Reason for error: Timeout: The call was not accepted. [Message]"
  • Internet (telephony) connection cleared.

Important:Some of the settings described here are only displayed if the advanced view is enabled in the user interface. The configuration procedure and notes on functions given in this guide refer to the latest FRITZ!OS

Simply proceed as described below. After each measure, check whether the issue persists.

1 The provider rejects the call attempt

This section only applies if the message "Internet telephony [...] failed. Reason for error: Not Acceptable Here (488)" is displayed under "System > Event Log" in the FRITZ!Box user interface when the error occurs. This message from your provider indicates that it does not make a requested function available for your line. This may be due to the following reasons, for example:

  • The provider does not support the requested codec.
  • The provider does not permit calls to the destination number, for example calls to premium numbers.
  • The provider does not allow you to make simultaneous calls.

Therefore, the FRITZ!Box cannot resolve this issue.

2 Entering your location information

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephone Numbers" in the "Telephony" menu.
  3. Click on the "Line Settings" tab.
  4. Select your country from the drop-down list under "Location Information". If your country is not included in the list, select "Other country".
  5. For the "Country code", enter the country code prefix in the first field and the country code in the second field (for example for Germany "00" and "49", see fig.).
  6. For the "Area code", enter the area code prefix in the first field and the area code in the second field (for example for Berlin "0" and "30", see fig.).

    Fig.: Entering the country code and area code (e.g. for Germany and Berlin)

  7. Click "Apply" to save your settings.

3 Restarting the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" or "Reset" in the "System" menu.
  3. Click on the "Restart" tab (if available).
  4. Click the "Restart" button.

4 Entering the correct Internet telephone number and account information

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephone Numbers" in the "Telephony" menu.
  3. Make a call and check whether the status LED before the number is green or gray.
    • Green LED:
      • The account information for your telephone number is correctly entered.
    • Gray LED:
      1. Change the password for your telephone number saved with your Internet telephony provider.

        Important:Use a password that you have not used before. Normally you can change your password in your personal customer area on your provider's website.

      2. Set up the telephone number in the user interface again.
      3. If the status LED is still gray, contact your Internet telephony provider to have your telephone number and account information checked.

5 Reconfiguring your telephone

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephony Devices" in the "Telephony" menu.
  3. Delete the telephone that cannot be used to make calls with. To do so, click the corresponding (Delete) button.
  4. Use the Wizard for telephony devices to reconfigure the telephone: To do so, click the "Configure New Device" button and follow the instructions.

6 Disabling HD telephony

  1. Click "DECT" in the FRITZ!Box user interface.
  2. Click "Cordless Telephones" in the "DECT" menu.
  3. Click the button (Edit) for the respective telephone.
  4. Click on the "Telephony Device Features" tab.
  5. Select the option "HD disabled" from the drop-down list in the "HD Telephony" section.
  6. Click "OK" to save the settings.

The FRITZ!Box is now completely configured for making calls over the Internet. If the issue persists, your Internet telephony provider may be experiencing technical difficulties.