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Knowledge document #42

Registering an IP telephone with the FRITZ!Box and setting it up

You can register a total of ten IP telephones with the FRITZ!Box. IP or SIP telephones are telephones for internet telephony (VoIP) and require an internet connection instead of a conventional telephone line. IP telephones are available as telephony devices (hardphones), as a combination of an adapter and a regular telephone, or as a software solution for your computer.

Requirements / Restrictions

  • The IP telephone has an IP address from the FRITZ!Box's IP address range.
  • IP telephones cannot be registered via guest access.
  • IP telephones cannot be used for fax and data connections.
  • Various FRITZ!Box functions cannot be used with IP telephones. This is the case with call transfer, busy on busy, call-back on busy / no response, individual do not disturb settings, accessing the telephone book, controlling certain FRITZ!Box functions such as enabling or disabling Wi-Fi, loading factory settings, or setting up call diversions, for example.

Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.

1 Configuring telephone numbers in the FRITZ!Box

Configure all of your telephone numbers in the FRITZ!Box:

Configuring internet telephone numbers

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

Configuring a landline number

  1. Configure the landline number in the FRITZ!Box.

Configuring a mobile telephone number

  1. Configure your mobile telephone number in the FRITZ!Box.

2 Connecting the telephone to the FRITZ!Box

  1. Either use Wi-Fi or a network cable to connect the telephone to the home network of the FRITZ!Box (not the guest network).

3 Configuring a telephone in the FRITZ!Box

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephony Devices" in the "Telephony" menu.
  3. Click the "Configure New Device" button.
  4. Enable the option "Telephone (with or without answering machine)" and click "Next".
  5. Enable the option "LAN/Wi-Fi (IP telephone)" and click "Next".
  6. Enter a password that is at least eight characters long and does not contain the username. Then, click "Next".
  7. Select the number the telephone should use for making calls and click "Next".
  8. Select the telephone numbers that the telephone should react to.
  9. Click "Next" and then "Apply" to save the settings.

4 Entering login information on the telephone

  1. On the telephone, configure an internet telephone number with the login information for the FRITZ!Box.
  2. Enter the username displayed in the FRITZ!Box user interface as the username for the telephone number.
  3. Enter the same password that you entered in the FRITZ!Box user interface.
  4. Enter or the IP address of the FRITZ!Box ( in the factory settings) as the SIP registrar. If you want to register the telephone with the FRITZ!Box over the internet, enter the public IP address of the FRITZ!Box as the SIP registrar instead.

    Note:Most internet service providers clear the internet connection on a daily basis ("automatic disconnection") and assign the FRITZ!Box a different IP address when the connection is automatically re-established. The FRITZ!Box can be accessed over the internet under its MyFRITZ! address at all times, even if its public IP address changes at regular intervals.

  5. Do not enter a STUN server.

Now you can use the telephone to make and receive calls using the telephone numbers you configured.

5 Configuring the telephone for registration from the internet

If you want to use the telephone in your home network as well as over the internet, you must allow registration from the internet:

ATTENTION!For security reasons, we recommend that you do not register IP telephones over the internet; instead, only register them over an encrypted VPN connection, for example over a VPN connection between two FRITZ!Boxes.

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephony Devices" in the "Telephony" menu.
  3. Click the (Edit) button for the respective telephone.
  4. Click on the "Account Information" tab.
  5. Enable the option "Allow registration from the internet".
  6. Click "OK" to save the settings.

6 Supported telephony functions

Normally you can use a number of FRITZ!Box functions using a telephone keypad. However, this only works to a limited extent with IP telephones. The functions CLIP (displaying caller's telephone number) and CLIR (blocking your telephone number from being displayed) can also be used when conducting calls with IP telephones. You can also conduct internal telephone calls with other telephones, pick up calls from other telephones connected to the FRITZ!Box, and use quick-dial numbers and vanity codes from the FRITZ!Box telephone book.

Note:You can find the internal numbers of the telephony devices under "Telephone Book > Internal Numbers" in the FRITZ!Box user interface.