My computer randomly loses its wired connection to a fairly new router, even though the Ethernet cable stays physically plugged in. This happened with both my old cable and a brand-new replacement. When it occurs, the computer switches to Wi‑Fi, disconnecting me from online games and making streaming impossible. Unplugging and reconnecting the cable restores the connection temporarily, but the problem eventually returns. What could be causing this, and how can I troubleshoot it?
2 Answers
Even a new cable can be defective or have a poorly fitting connector, so test with another known-good cable if possible. Try a different port on the router as well. Ethernet cables are generally compatible with modern routers, so Cat5e or Cat6 should work; incompatibility is unlikely. If another cable and router port behave the same way, the computer’s network adapter or its driver becomes the more likely culprit.
This may be the computer’s Ethernet adapter entering a power-saving state and failing to wake up properly. Update the adapter’s driver, then open its properties in Device Manager and disable options such as “Allow the computer to turn off this device to save power.” Also check your Windows power plan and turn off aggressive network or PCIe power-saving settings. Choosing “Best performance” can help, but the adapter-specific setting is worth checking too.
I changed the power plan from Balanced to Best performance, so I’ll also check the Ethernet adapter’s properties and update its driver.

That makes sense. I’ll test another router port and cable, although reconnecting the current cable temporarily restoring the connection still makes me suspect the adapter or its driver.