FRITZ!Box 4020 Service - Knowledge Base
LAN connection to FRITZ!Box cannot be established
One or more of the LAN ports cannot be used to establish a connection 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 issue persists.
1 Restarting the FRITZ!Box
- Unplug the FRITZ!Box for 5 seconds.
Note:The FRITZ!Box settings remain intact. The restart will take 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:
- Install the latest FRITZ!OS on your FRITZ!Box.
3 Installing the latest software for network adapters
- Install the latest driver for your computer's LAN network adapter or the latest software for the device.
Note:Often the Windows Update does not offer all of the latest device drivers. Therefore, use the drivers from the manufacturer's website (for example Intel, Broadcom, Realtek).
4 Connecting the device directly to the FRITZ!Box
Perform the following step if the device is connected by means of a hub/switch, powerline adapter, LAN/wireless LAN converter, or other devices instead of being connected directly to the FRITZ!Box:
- Connect the device directly to a LAN port on the FRITZ!Box. If possible, use the yellow cable included with the FRITZ!Box.
- If you can now establish a LAN connection to the FRITZ!Box, then the intermediary device or its cabling was causing the problem:
- Make sure that any intermediary devices function properly.
- Update the software / firmware of all intermediary devices.
- Use a different, short network cable to connect the devices to the FRITZ!Box.
5 Testing a different cable
The device may be connected to the FRITZ!Box by means of a network cable that is too long, incorrectly wired, or defective:
- Use a high-quality network cable that is as short as possible (for example the yellow cable included with the FRITZ!Box) to connect the device to the FRITZ!Box.
Note:Any standard STP-type (Shielded Twisted Pair, 1:1) CAT5e Ethernet cable that is no longer than 100 m can be used to connect a device to the FRITZ!Box.
6 Disabling energy-saving functions for the network adapter
- If energy-saving functions are enabled for the computer's LAN network adapter or the device, disable them for testing purposes.
Note:In Windows, many LAN network adapters allow you to select various energy-saving options in the Windows Device Manager. You can find these settings on the "Power Management" tab in the properties of the network adapter.
7 Testing a different LAN port
- 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 your FRITZ!Box.
- If your device can access the FRITZ!Box and the internet when connected to a different LAN-port, use that LAN port instead.
8 Testing a different device
- Connect a different device to the LAN port on the FRITZ!Box.
- If the other device can access the FRITZ!Box and the internet, then the first device is either incorrectly configured or defective.