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Knowledge document #1083

Cannot access FRITZ!Box home network using port sharing

Although port sharing is configured, you cannot access devices in the FRITZ!Box home network, for example a NAS system, a web server, or remote maintenance server from the internet.

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

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

1 Public IP address required for access

You can only access devices in the FRITZ!Box home network over the internet if the FRITZ!Box obtains a public IPv4 address or an IPv6 address from your internet service provider when it connects to the internet.

Access via IPv4

For IPv4 internet access, the FRITZ!Box must obtain a public IPv4 address from the internet service provider. Access over IPv4 is not possible if the FRITZ!Box obtains a private IPv4 address.

You can find out whether the FRITZ!Box obtained a public or private IPv4 address by following the steps in our guide Identifying the address range of the IPv4 address for the internet connection.

Access via IPv6

For IPv6 internet access, both the FRITZ!Box and the device that is to access the FRITZ!Box must be connected to the internet over IPv6. If only the FRITZ!Box obtains an IPv6 address but the other device is not connected to the internet via IPv6, IPv6 internet access is not possible.

You can call up the menu "Internet > Online Monitor" in the FRITZ!Box user interface to determine whether the FRITZ!Box is connected to the internet via IPv6.

You can test whether the device that is to access the FRITZ!Box is connected to the internet over IPv6 by calling up www.test-ipv6.com or www.ipv6-test.com on the device.

2 Maintaining a permanent internet connection

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Account Information" in the "Internet" menu.
  3. Click "Change connection settings".
  4. Enable the option "Maintain permanently (recommended for flat rates)". If the option is not shown, the FRITZ!Box is already permanently connected to the internet.
  5. Click "Apply" to save the settings.

3 Configuring parental controls to allow internet access

You cannot access devices in the home network over the internet if the FRITZ!Box parental controls restrict the device's internet access. Therefore, make sure that the respective devices are allowed to access the internet:

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Filters" in the "Internet" menu.
  3. Click on the "Parental Controls" tab.
  4. Check whether internet use has been restricted for the device you want to access.
  5. If internet use has been restricted or blocked for the device, configure the parental controls for the device so that it has unrestricted internet access.

4 Disabling the NetBIOS filter

The following step is only necessary if you want to access shared files and printers in the home network over the internet and your internet service provider does not block TCP and UDP ports 139 and 445 that are used for this:

Important:For security reasons, the FRITZ!Box and some internet service providers (for example in the cable and mobile networks) block access from the internet to the ports used for file and printer sharing ("NetBIOS Filter"). Therefore, only disable the NetBIOS filter in the FRITZ!Box if a firewall is set up on each of the devices.

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Filter" in the "Internet" menu.
  3. Click on the "Lists" tab.
  4. Disable the option "NetBIOS filter enabled". If the option is not displayed, enable the Advanced View first.
  5. Click "Apply" to save the settings.

5 Configuring the device's firewall

If the server service or application is installed on a device with its own firewall (for example Windows firewall), the firewall must also be configured:

  1. Configure the device's firewall according to the manufacturer's instructions to allow access to the server service or application from the FRITZ!Box home network.

Now the FRITZ!Box is fully configured so that the FRITZ!Box or devices or server services in the FRITZ!Box home network can be accessed over the internet. If the issue persists, inappropriate settings or errors in the relevant application or device may be the cause.

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