FRITZ!Box 6840 LTE Service - Knowledge Base

FRITZ!Box 6840 LTE Service

Cannot access FRITZ!Box home network using port sharing

You cannot access the FRITZ!Box, or server services or network devices in the FRITZ!Box home network (for example HTTP server, remote maintenance server, NAS system) over the Internet although port sharing is configured.

Important:Some of the settings described here are only displayed if the advanced view is enabled in the user interface. The configuration procedure and notes on functions given in this guide refer to the latest FRITZ!OS

Simply proceed as described below. After each measure, check whether the issue persists.

1 Checking whether a public IP address was obtained

You can only access the FRITZ!Box, or server services or network devices in the FRITZ!Box home network from the Internet if your Internet service provider assigns the FRITZ!Box an IP address from the public address range when it connects to the Internet:

  • Check the address range of the IP address assigned by your Internet service provider.
    • If the FRITZ!Box obtained an IP address from the public address range:
      • Proceed with the following section.
    • If the FRITZ!Box obtained an IP address from the private address range:
      • You cannot access the FRITZ!Box, or server services or network devices in the FRITZ!Box home network over the Internet.

2 Setting up port sharing in the FRITZ!Box

Setting up static port sharing

The following step is only necessary if you did not configure static port sharing for the server service or the network device:

Note:If static port sharing is not configured for the server service or the network device, other Internet applications or network devices may be able to configure the necessary port sharings for themselves using the UPnP standard (Universal Plug and Play).

Deleting multiple port forwardings to the same destination port

You cannot access different devices in the home network over the Internet if packets being sent to the same port (destination port) on the FRITZ!Box are supposed to be forwarded to different IP addresses in the home network.

If you forward a given destination port in the FRITZ!Box more than once, then the first port forwarding rule to be used deactivates all of the other port forwarding rules that apply to this destination port. Other port forwardings are blocked from using this destination port until it has not been accessed for 15 minutes.

Example:
In the FRITZ!Box you forwarded port 80 to port 80 for a web server, and you also forwarded port 81 to port 80 for a NAS system. If the NAS system is accessed over the Internet, then the web server can no longer be reached.

Use a different destination port for each port forwarding. Otherwise you may not be able to or sometimes may not be able to access certain server services or network devices:

  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. Check whether there are several ports opened to the same destination port ("to Port") in the "List of Shared Ports".
    • If more several port forwardings are configured to the same destination port:
      1. Configure the server services or network devices to use a port that is not used by other devices in the FRITZ!Box home network.
      2. Click the button (Edit) next to all port forwardings to the same destination port and enter a new port number for "to Port".

        Example:
        Configure port sharing from port 80 to port 80 for your web server. Configure port sharing from port 81 to port 81 for the user interface of your NAS system and adjust its settings so that you can use port 81 to open the user interface.

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 would like to access.
    • If the device has unrestricted access to the Internet:
      • Proceed with the following section.
    • If Internet access has been restricted or blocked for the device:
      • Configure the parental controls for the device so that it has unrestricted use of the Internet.

4 Disabling the NetBIOS filter

The following step is only necessary if you would like to use the SMB or CIFS protocol to establish connections to network devices in the FRITZ!Box home network (for example in order to access shared files or printers over the Internet):

ATTENTION!The FRITZ!Box filters TCP and UDP ports 139 and 445 ("NetBIOS filter") because they are often used to attack computers and these ports are normally not required for communication in the Internet. Only disable the NetBIOS filter if a firewall is set up on each of the computers.

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Filters" in the "Internet" menu.
  3. Click on the "Lists" tab.
  4. Disable the option "NetBIOS filter enabled".
  5. Click "Apply" to save your settings.

5 Configuring the computer's firewall

If the server service or Internet application is installed on a computer with its own firewall (for example Windows firewall), you must also configure the firewall:

  • Configure the computer's firewall so that the server service or Internet application can be accessed from the FRITZ!Box home network.

    Note:You can find information on configuring the firewall in its manual, or consult its manufacturer directly.

Now the FRITZ!Box is completely configured so that the FRITZ!Box and server services or network devices in the FRITZ!Box home network can be accessed over the Internet.

Note:If the issue persists, the application or network device in the FRITZ!Box home network or Internet may be incorrectly configured.