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Knowledge document #835

Shared files and printers on a computer are not available over the internet

You cannot access shared files and printers on remote computers over your FRITZ!Box's internet connection. Other connections using the SMB or CIFS protocol cannot be established over the FRITZ!Box's internet connection either, for example connections to Strato HiDrive. It is also not possible to establish connections from the internet to the home network if the SMB or CIFS protocol is used.

Cause

  • 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 TCP and UDP ports 139 and 445 that are used for file and printer sharing ("NetBIOS Filter").

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

Accessing shared files and printers without NetBIOS

  1. You can access the files or printers through an application that uses secure transfer protocols such as HTTPS or SFTP instead of the SMB or CIFS protocol ("NetBIOS"), or you can use a VPN connection to access the remote network.

Workaround

If it is not possible to access the shared files and printers without NetBIOS and the internet service provider does not block NetBIOS, you can disable the NetBIOS filter in the FRITZ!Box instead:

Important:When the NetBIOS filter is disabled, devices in the home network may be subject to more frequent attacks from the internet. Therefore, set up a firewall on all of the devices in the home network.

  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.
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