Setting up a DMZ with the FRITZ!Box

1. Click "Internet" in the FRITZ!Box user interface.
2. Click "Permit Access" in the "Internet" menu.
3. Click on the "Port Sharing" or "Port Forwarding" tab.
4. Click the  (Edit) button for the (computer) name of the device that you want to set up an exposed host for. If you have not configured any sharings for the device yet:
   1. Click "Add Device for Sharing".
   2. Select the (computer) name of the device from the drop-down list "Device".

      Note:If you cannot select the device, you can select "Enter the IP address manually" and enter the IP address. Only devices that automatically obtain their IP settings (DHCP) from the FRITZ!Box are listed in the drop-down list.

5. Enable the option "Open this device completely for internet sharing via IPv4 (exposed host)".
6. If the device supports the IPv6 protocol and you also want to set up the exposed host for IPv6 internet access, enable the option "Open this device completely for internet sharing via IPv6 (exposed host)".

   Note:This option is only displayed if IPv6 support is enabled in the FRITZ!Box under "Internet > Account Information > IPv6".

7. Click "OK" to save the settings.

https://en.avm.de/service/knowledge-base/dok/FRITZ-Box-7490/131_Setting-up-a-DMZ-with-the-FRITZ-Box/