LAN not working – Realtek Network Controller not found

Troubleshooting LAN Connectivity Issues: Realtek Network Controller Not Detected on Asus B450M-Dragon Motherboard

Encountering network connectivity issues can be frustrating, especially when your system fails to recognize your LAN hardware. If you’ve recently powered on your PC after a prolonged period and find that your LAN is not working—specifically, the Realtek Network Controller isn’t detected—this guide provides step-by-step troubleshooting tips to help you resolve the issue efficiently.

Problem Overview
After rebooting your computer, you notice that the LAN connection isn’t functioning. Despite the network cable being properly connected (indicated by the orange LED), your system fails to recognize the network controller. Common symptoms include error messages when attempting to install drivers, such as:

“Realtek Network Controller was not found. If Deep Sleep Mode is enabled, please plug the cable in.”

Key Troubleshooting Steps

1. Verify Hardware Connections
2. Ensure that the Ethernet cable is securely connected to both your PC and the router or switch.
3. Check the Ethernet port for physical damage or debris.

4. Confirm that the cable itself is functional by testing with another device or using a different cable.

5. Inspect BIOS Settings

6. Reboot your PC and enter the BIOS configuration.
7. Verify that the integrated LAN controller is enabled.

8. Save any changes and exit BIOS.

9. Confirm Operating System Recognizes Hardware

10. Access Device Manager (Windows) and look under “Network Adapters.”

11. If the Realtek network controller is missing or shows a warning icon, driver issues may be present.

12. Manually Install or Update Drivers

13. Download the latest drivers for your motherboard’s LAN controller from the official ASUS support website.
14. Perform a clean driver installation:
15. Uninstall existing drivers.
16. Restart your PC.
17. Install the downloaded drivers.

Note: During driver installation, you might encounter the error:
“Realtek Network Controller was not found. If Deep Sleep Mode is enabled, please plug the cable in.”

1. Address Deep Sleep Mode-Related Issues
2. The error message suggests that the system may be in a deep sleep or low-power state affecting the LAN device.
3. To mitigate this:
4. Disconnect power from your PC.
5. Press and hold the power button for at least 30 seconds to discharge residual power.
6. Plug the system back in and power it on.

7. Alternatively, disable deep sleep mode in BIOS or power management settings within Windows.

8. Test with Different Hardware