My PC has an onboard Realtek Ethernet adapter on a Gigabyte H610M K DDR4 Rev. 2.0 motherboard. The wired connection randomly stops working, and when it happens, the LAN port LEDs go completely dark even though the adapter remains listed in Device Manager. It sometimes reconnects on its own after a few minutes, and disabling and re-enabling the adapter has occasionally restored the connection. I have already updated the Realtek driver, tested another Ethernet cable and router port, disabled power-saving and EEE features, and tried manually setting the adapter to 100 Mbps Full Duplex instead of Auto Negotiation. The driver update appeared to help for a few days, but the disconnects have returned and are becoming more frequent. Does this sound like a failing onboard LAN controller or motherboard, or are there other tests I should perform before requesting a warranty replacement?
4 Answers
The router could still be involved. Put an inexpensive unmanaged network switch between the PC and router. Your internet connection might still fail if the router is the problem, but the PC should retain an active Ethernet link. If the Ethernet link itself stays up through the switch, the router or its port becomes more suspicious.
Boot from a Linux live USB, such as Ubuntu, and use the connection normally for a while. If the Ethernet link and port LEDs fail in Linux too, that largely rules out Windows and its drivers and points toward the adapter, motherboard, cable, or network hardware. Depending on how the USB is created, Secure Boot might need to be disabled.
Try a separate Ethernet adapter as a practical test. A USB 3.x-to-Ethernet adapter is usually fast enough for normal use, while a PCIe Ethernet card is another option. If the external adapter remains stable using the same cable and router port, the motherboard's onboard LAN becomes the likely culprit. If available, also check that its transmit and receive buffers are set reasonably high.
The fact that the physical port LEDs turn off is a strong hardware warning. Disabling and re-enabling the adapter resets the network chip and can temporarily bring a marginal controller back to life, so the temporary improvement from a driver update does not rule out failing hardware. If the LEDs also go out while running Linux, I would consider the onboard LAN controller or motherboard defective and use the warranty.
If Linux shows the same behavior, that would be much stronger evidence of a hardware fault than another Windows driver reinstall.
That seems like the most useful next step. Testing outside Windows should help separate a software problem from a hardware one.