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Knowledge document #1638

Setting up a public IPv4 subnet in the FRITZ!Box

The FRITZ!Box can also be used on an internet connection with multiple fixed ("static") public IPv4 addresses. This way you can offer your server services or internet applications in the internet under different public IP addresses.

Requirements / Restrictions

  • The internet service provider must supply you with a public IPv4 subnet for your internet connection. The FRITZ!Box uses the first IPv4 address of the IPv4 subnet for itself; the other IPv4 addresses can be used by devices in the home network.

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

1 Setting up a public IPv4 subnet in the FRITZ!Box

  1. Click "Home Network" in the FRITZ!Box user interface.
  2. Click "Network" in the "Home Network" menu.
  3. Click on the "Network Settings" tab.
  4. Click "Additional Settings" in the section "WAN setting" or "LAN Settings" to display all of the settings.
  5. Click the "IPv4 Settings" button.
  6. Enter the public IPv4 subnet that you received from your internet service provider in the "Prefix" and "Network mask" fields in the "Public IPv4 Subnet" section.
  7. Click "Apply" to save the settings.

2 Configuring a network device

Adjust the IP settings of all of the network devices that should be accessible at an IP address from the FRITZ!Box's public IPv4 subnet:

Note:Network devices that are assigned a public IP address no longer obtain their IP settings from the FRITZ!Box. Therefore, they cannot access other devices in the FRITZ!Box home network or the FRITZ!Box user interface.

  1. For the IP address, enter an IP address from the public IPv4 network. This IP address may not already be used by another device in the FRITZ!Box home network.
  2. For the subnet mask, enter the subnet mask that corresponds to the public IP address.
  3. If necessary, enter one of the internet service provider's default gateways as the default gateway.
  4. As the preferred and alternative DNS server, enter the DNS server of the internet service provider.

3 Setting up port sharing in the FRITZ!Box

Configure port sharing in the FRITZ!Box for the IP addresses from the public IPv4 subnet so that your server services or internet applications can be reached in the internet:

Important:Port sharing can only be configured if there is no entry for the device in the network overview of the FRITZ!Box with a previous DHCP configuration.

Preparations

  1. Disconnect the device from the FRITZ!Box for which you would like to configure port sharing.

Deleting the device from the user interface

  1. Click "Home Network" in the FRITZ!Box user interface.
  2. Click "Network" in the "Home Network" menu.
  3. Click on the "Network Connections" tab.
  4. If the device for which you wish to configure port sharing is displayed in the "Idle Connections" section, click the (Delete) button next to the device.

Configuring port sharing

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Permit Access" in the "Internet" menu.
  3. Click on the "Port Sharing" tab.
  4. Click "Add Device for Sharing".
  5. Select "Enter the IP address manually" from the drop-down list "Device".
  6. In the "IPv4 address" field, enter the public IP address that you assigned to the device.
  7. Click "New Sharing".
  8. Enable the option "Port Sharing".
  9. Select "Other application" from the drop-down list "Application".
  10. Enter a name of your choice for the port sharing rule in the "Name" field.
  11. Select the IP protocol (TCP, UDP, ESP or GRE) required by the server service or internet application from the drop-down list "Protocol".

    Note:The IP protocols ESP and GRE are only required for VPN server services.

  12. To enable port sharing for a single port, enter the number of the port used by the server service or internet application to accept connections in the "Port to device", "to port", and "Port requested externally" fields.
    • To enable port sharing for a port range:
      1. In the "Port to device" field, enter the number of the first port used by the server service or internet application to accept connections, and in the "to port" field, enter the number of last port.
      2. In the "Port requested externally" field, enter the number of the first port used by the server service or internet application to accept connections.
  13. Enable the sharing.
  14. Click "Apply" to save the settings.
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