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Knowledge document #177

Conducting calls with the FRITZ!Box over another router

You can also use the FRITZ!box to conduct calls if another router (for example an IAD) in the network establishes the internet connection. You can use any internet telephony provider from which you received login information for internet telephone numbers. The telephone numbers can either be from your provider or from a different internet telephony provider.

1 Configuring internet telephone numbers

  1. Configure the internet telephone numbers in the FRITZ!Box.

2 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.

3 Setting up port forwarding for internet telephony

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:

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/SRTP, for example Telekom, Easybell,, also configure port forwarding from TCP port 5061 to port 5061 on the FRITZ!Box.

Now you can assign your telephone numbers to the telephony devices connected to the FRITZ!Box and use them for making and receiving calls.