A totally dark Ethernet port looks like dead hardware. Most of the time it is not. Work this ladder from the cheapest check to the rarest fault, and only replace the part the evidence convicts.
No light means no electrical handshake happened at all. That is actually good news for diagnosis: the list of things that can prevent a handshake is short - cable, connector, port, adapter state, or the far end being off. Resist the urge to reinstall Windows; a missing link light is below Windows, at the physical layer. If your light exists but keeps dropping instead, that is the flapping problem covered in the main fix guide - this page is for the port that shows nothing, ever.
Patch cables fail quietly: a broken conductor inside the jacket, a plug whose clip snapped so it sits half a millimetre out, or contacts corroded by humidity.
If the light wakes with a different cable, you are done - throw the old cable away so it never wastes another hour.
Individual switch ports die, get disabled by an administrator, or - on managed switches - can be shut down by security features after a fault. Move your cable to a port you know works, ideally the one a working PC just used. If your PC lights up there, the old port is the problem, not your computer. In an office, tell the IT team the port number instead of just 'the LAN is dead' - it saves them the same ladder.
A port with a perfectly good cable still shows no light if the adapter is disabled:
ncpa.cpl and Enter. If the Ethernet adapter is greyed out, right-click and Enable it.Follow the cable mentally to its other end. Is the switch powered on? Does the same switch light up for other PCs? For a wall socket in an office, the cable disappears into the wall and reappears in a rack - a disconnected patch lead in that rack leaves your wall port dead even though everything at your desk is perfect. Testing your PC directly at the switch with a short cable separates 'my PC' from 'the building wiring' in one move.
Ports do fail - a nearby lightning strike, a power surge, or years of heat can kill the network chip while the rest of the PC works fine. The honest verdict test: known-good cable, known-good switch port, adapter enabled everywhere, still no light on any combination. At that point stop spending time: a USB-to-Ethernet adapter or a PCIe network card restores wired networking in minutes for little money, and on a laptop the USB adapter is the only practical route. Replacing the motherboard for one dead port is rarely sensible.
See the adapter settings changed live, step by step, in the full Technical Anshu video.
Watch Full VideoNot necessarily. Wi-Fi and wired Ethernet are separate chips with separate drivers. A dead wired port usually affects only wired networking. Work the ladder first - cables and disabled adapters are far more common than a dying board.
An update can disable or break the adapter driver, which shows as no link in Windows - check Device Manager for warning marks. But no software can stop the physical link light on a healthy port when a live cable is attached and the adapter is enabled in BIOS. If the adapter is missing from Device Manager entirely, suspect BIOS settings or hardware.
The building wiring between the rack and your wall socket - the cable inside the wall, a punch-down connection, or the socket itself. That is a cabling job, not a PC fault, and it is exactly the kind of thing to report with the socket number.