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Knowledge document #119

Parties cannot hear each other

When conducting calls, one of the following issues either occasionally occurs or always occurs. It either occurs right at the beginning of the conversation or sometime during the conversation, for example after five minutes:

  • You do not hear the other party.
  • The other party does not hear you.
  • The parties cannot hear each other.

This may give the impression that the telephone connection has been terminated. However, the connection is still active. You can see that it is because the telephony LED on the FRITZ!Box remains lit. The LED does not switch off until you end the call by hanging up.

Simply proceed as described below. After each measure, check whether the problem is solved.

1 Installing the latest software

  1. Install the latest software on the telephone.

2 Restarting the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" in the "System" menu.
  3. Click on the "Restart" tab.
  4. Click the "Restart" button.

3 Entering a STUN server

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephone Numbers" in the "Telephony" menu.
  3. Click the (Edit) button for the respective internet telephone number.
  4. Check if the field "STUN server" is present under the fields for entering your login information.
  5. If the field is present and empty, enter the address of your internet telephony provider's STUN server and click "OK".
    • If the field is not present:
      1. Select "Other provider" from the drop-down list, even if you are using a preconfigured internet telephony provider.
      2. Check if the "STUN server" field is present now.
      3. If the field is present, enter the address of your internet telephony provider's STUN server and click "OK".
        • If the field is not present, click "Cancel". The STUN server is already preconfigured.

4 Setting up port forwarding for internet telephony

The following steps are only necessary if the FRITZ!Box does not establish its own connection to the internet, and uses the internet connection of another router in the network instead:

Setting up automatic port forwarding

If you enable port forwarding in the FRITZ!Box, the FRITZ!Box sends IP packets at regular intervals and the router's port forwarding automatically remains enabled:

  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. Click "Changing the Settings" in the "Telephony connection" section.
  5. Enable the option "Keep port sharing of the internet router enabled for telephony".
  6. Select a suitable time interval. Select "30 sec." if you do not know how long temporary port forwarding rules will be maintained.
  7. Click "Apply" to save the settings.

Setting up static port forwarding

The following steps are only necessary if the router does not support automatic port forwarding by the FRITZ!Box:

Note:Refer to the manufacturer of the router for information on setting it up; for example, consult the manual.

  1. On the router, configure port forwarding from UDP port 5060 to port 5060 on the FRITZ!Box.
  2. If your telephony provider supports encrypted telephone calls via TLS, for example Telekom, Easybell, dus.net, also configure port forwarding from TCP port 5061 to port 5061 on the FRITZ!Box.

The FRITZ!Box is now fully configured for making and receiving calls over the internet. We are not aware of any additional measures to correct this error. If you still experience the problem, your internet telephony provider may be experiencing technical difficulties or the router that establishes the internet connection may not be forwarding the voice packets to the FRITZ!Box, for example. In these cases, a solution on the part of the FRITZ!Box is not possible.

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