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Knowledge document #318

LAN connection to FRITZ!Box cannot be established

One or more of the LAN ports cannot be used to connect to the FRITZ!Box. The FRITZ!Box does not detect computers, NAS systems, or other network devices connected to it and they cannot access the FRITZ!Box or the internet. One of the following error messages may be displayed by the device:

  • "A network cable is unplugged."
  • "Network cable unplugged."
  • "You are currently not connected to any networks."

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

1 Restarting the FRITZ!Box

  1. Unplug the FRITZ!Box for 5 seconds.

    Note:The FRITZ!Box settings are retained when you unplug it. The restart takes about 2 minutes. During this time, you cannot access the FRITZ!Box.

2 Installing the latest FRITZ!OS

Perform the following steps on a different device connected to the FRITZ!Box:

Important:If you cannot access the FRITZ!Box with any device, proceed as described in the guide FRITZ!Box user interface cannot be opened.

  1. Install the latest FRITZ!OS on the FRITZ!Box.

3 Installing the latest software for the device

  1. Install the latest software version for the device or the latest driver for the computer's LAN network adapter.

    Note:Since Windows Update often does not offer the latest drivers, install the drivers from the manufacturer's website, for example from the Intel Download Center.

4 Connecting the device directly to the FRITZ!Box

This step is only necessary if the device is connected to the FRITZ!Box by means of a hub/switch, powerline device, LAN/Wi-Fi converter, or other device instead of being connected directly to the FRITZ!Box:

  1. Connect the device directly to a LAN port on the FRITZ!Box. If possible, use the yellow cable included with the FRITZ!Box.
  2. If you can establish a LAN connection to the FRITZ!Box now, then there is a problem with the intermediary device or its cabling:
      1. Make sure that the intermediary devices function properly.
      2. Update the software / firmware of the intermediary devices.
      3. If the intermediary devices offer different network or routing settings, test them. For example, disable advanced options like STP / MSTP for testing purposes.
      4. Use different network cables to connect the devices to the FRITZ!Box. Use the shortest possible high-quality network cables (CAT 5e or higher).

5 Testing a different cable

The network cable used to connect the device to the FRITZ!Box may be too long, incorrectly wired, or defective:

  1. Use the shortest possible high-quality network cable to connect the device to the FRITZ!Box, for example use the network cable included with the FRITZ!Box.

    Note:Any standard network cable CAT 5e or higher (STP, 1:1) with a maximum length of 100 m can be used to connect network devices to the FRITZ!Box.

6 Adjusting the WAN setting of the FRITZ!Box

The following step is only necessary if the FRITZ!Box does not use the WAN port to establish the internet connection and the device is connected to the WAN port on the FRITZ!Box:

  1. Open the FRITZ!Box user interface on a device that is not connected to the WAN port on the FRITZ!Box.
  2. Click "Network" in the "Home Network" menu.
  3. Click on the "Network Settings" tab.
  4. Enable the option "LAN 4" in the section "WAN setting". If the option is not shown, the FRITZ!Box establishes the internet connection via the WAN port. In this case, the WAN port cannot be configured as a LAN port.
  5. Click "Apply" to save the settings.

7 Disabling energy-saving functions for the network adapter

  1. If any energy-saving functions are enabled for the computer's LAN network adapter or the device, disable them for testing purposes.

    Note:In Windows, different power saving functions can be set for many network adapters under "Properties > Power Management" in the Device Manager.

8 Disabling EEE (Energy Efficient Ethernet) in the FRITZ!Box

With EEE, network adapters can be put into an energy-saving standby mode, thus also significantly reducing their average power consumption. Since there may be compatibility issues with individual network adapters when EEE is enabled, disable EEE for testing purposes:

Links "Help and Info" and then "FRITZ!Box Support"
  1. In the FRITZ!Box user interface, click "Help and Info" on the bottom left of the page and then on "FRITZ!Box Support" at the bottom.
  2. Enable the option "Disable EEE (Energy Efficient Ethernet)" in the "Ethernet Compatibility" section.
  3. Click "Apply setting" to save the settings.

9 Connecting a 10BASE-T device using a cross cable

The following step is only necessary if the respective device is connected to the FRITZ!Box via a 10 Mbit/s (10BASE-T) network adapter:

  1. Use a cross cable or crossover network cable (network cable with twisted cable pairs) to connect the device to a LAN port on the FRITZ!Box.

    Note:Many devices with 10BASE-T network adapters (for example measuring instruments, smart home devices, or internet of things devices) do not support auto MDI/MDI-X and therefore need cross cables. Cross cables can be purchased from electronics retailers.

10 Adjusting the FRITZ!Box's LAN settings

Problems may occur when negotiating transmission rates. Therefore, test whether the connection can be established when you adjust the settings for the LAN port:

  1. Open the FRITZ!Box user interface on a different device.
  2. Click "Network" in the "Home Network" menu.
  3. Click on the "Network Settings" tab.
  4. If "Green Mode" is enabled in the section "LAN Settings" for the LAN port being used, enable "Power Mode".
    • If "Power Mode" is enabled for the LAN port being used, enable "Green Mode".
  5. Click "Apply" to save the settings.

11 Testing a different LAN port

  1. For testing purposes, use a network cable that is as short as possible (for example the yellow cable included with the FRITZ!Box) to connect the device to the other LAN ports on the FRITZ!Box.
  2. If your device can access the FRITZ!Box and the internet when connected to a different LAN port, use that LAN port instead.

12 Testing a different device

  1. Connect a different device to the LAN port on the FRITZ!Box.
  2. If the other device can access the FRITZ!Box and the internet, the first device is either incorrectly configured or defective.



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