How to Fix Ethernet Not Working

Ethernet not working most often results from a faulty or loose network cable rather than a problem inside Windows. Other frequent causes include a dead router or switch port, a network adapter disabled in Network Connections, an outdated or corrupt Ethernet driver, a wrong or expired IP address from DHCP, a speed and duplex mismatch on the port, and an onboard LAN controller disabled in the BIOS. This article covers a wired connection that fails to carry traffic, separate from wireless drops and a full network outage.

It first lists the specific causes of a dead Ethernet link, then gives step-by-step fixes ordered from a cable check to a BIOS setting. Each fix names the exact tool to use, including the cable link lights, Network Connections, Device Manager, and the adapter Advanced settings.

Apply the fixes in order and check the link after each one, because a single fault usually accounts for the dead connection. The goal is a restored wired link without replacing the network card.

What Causes Ethernet Not to Work?

Ethernet not working is caused by a break in the wired path or a disabled component between the computer and the router. The causes below are ranked from most to least common on Windows.

• A faulty or loose Ethernet cable. A damaged cable or a connector that is not fully seated breaks the wired link before any data flows.
• A dead router or switch port. A failed port on the router or switch carries no signal even when the cable and adapter work.
• A disabled network adapter. An Ethernet adapter switched off in Network Connections shows no connection at all.
• An outdated or corrupt driver. A faulty Ethernet driver stops the adapter from forming a working link.
• A wrong or expired IP address. A failed DHCP lease leaves the wired adapter with no valid address to route traffic.
• A speed and duplex mismatch. A forced port speed that the adapter and switch do not share causes a dropped or dead link.
• A disabled onboard LAN. An onboard network controller turned off in the BIOS hides the Ethernet adapter from Windows entirely.

Check the Cable and Link Lights

Inspecting the cable and the port link lights confirms whether the physical wired connection is live, which is the first check for any dead Ethernet link. The lights sit beside the Ethernet port on the computer and the router.

1. Confirm the cable clicks fully into the port on both the computer and the router.
2. Look for a solid or blinking link light at both Ethernet ports.
3. Treat a dark link light at both ends as a cable, port, or adapter fault.
4. Reseat the cable at both ends and watch for the link light to turn on.
5. Run the cable along a different path away from power cables to rule out interference.

A link light that stays dark on both ports points to the cable or the adapter. A link light on one end only points to a fault in the cable or the device at the dark end.

Try Another Cable and Port

Swapping the cable and the port isolates whether the fault is in the cable, the router port, or the computer, which a single change cannot reveal. A spare cable and a second port give a fast comparison.

1. Replace the Ethernet cable with a known-good cable rated Cat 5e or higher.
2. Move the cable to a different LAN port on the router or switch.
3. Connect the cable to a second device, such as a laptop, to test the same cable and port.
4. Note whether the link light returns after each change.
5. Treat a working link on the second device as a fault on the first computer, not the cable.

A cable that works on a second device but not the first confirms the fault is inside the first computer. A cable that fails on every device confirms a damaged cable or a dead router port.

Enable the Ethernet Adapter in Network Connections

Enabling the Ethernet adapter restores a connection that shows nothing because the adapter was switched off in Network Connections. A disabled adapter appears greyed out in the connections list.

1. Press Windows plus R, type ncpa.cpl, and press Enter to open Network Connections.
2. Find the Ethernet adapter in the list.
3. Right-click the adapter and select Enable when it appears greyed out.
4. Right-click the adapter again and select Diagnose to run the network troubleshooter.
5. Confirm the adapter status changes to a connected network name.

An adapter that is already enabled but shows a red X has no cable signal, which returns the check to the cable and port. An adapter missing from the list entirely points to a driver or a disabled onboard LAN.

Reinstall the Ethernet Driver

Reinstalling the Ethernet driver replaces corrupt code that prevents the wired adapter from forming a working link. Device Manager lists the wired adapter under Network adapters with the controller name.

1. Right-click the Start button and select Device Manager.
2. Expand Network adapters and find the Ethernet or LAN controller.
3. Right-click the adapter and select Uninstall device.
4. Restart the computer so Windows reinstalls the default driver automatically.
5. Download the latest driver from the motherboard or PC maker when the link stays dead.

A wired adapter marked with a yellow warning icon in Device Manager confirms a driver fault. The motherboard maker publishes the correct LAN driver for the onboard Realtek or Intel controller, which resolves faults the generic Windows driver does not.

Renew the IP Address and Flush DNS

Renewing the IP address and flushing DNS restores traffic when the wired link is live but a failed DHCP lease left the adapter without a valid address. Both commands run in an elevated Command Prompt.

1. Type cmd in Windows Search, right-click Command Prompt, and select Run as administrator.
2. Run ipconfig /release to drop the current wired IP address lease.
3. Run ipconfig /renew to request a fresh address from the router DHCP server.
4. Run ipconfig /flushdns to clear the stored DNS records.
5. Run ipconfig /all and confirm the Ethernet adapter shows a valid IPv4 address and gateway.

A wired adapter showing a 169.254 address after a renew reached no DHCP server, which returns the check to the cable, the port, or the router. A valid 192.168.x.x address with a matching gateway confirms the lease and the physical link both work.

Set the Network Speed and Duplex to Auto

Setting the adapter speed and duplex back to auto-negotiation fixes a dead or dropping link caused by a forced speed the adapter and switch do not share. The setting sits on the Advanced tab of the adapter properties.

1. Open Device Manager and double-click the Ethernet adapter.
2. Open the Advanced tab.
3. Select the Speed and Duplex property in the list.
4. Set the value to Auto Negotiation.
5. Click OK and confirm the link returns at the negotiated speed.

A link forced to 1.0 Gbps Full Duplex on one end and auto on the other can fail entirely. Auto-negotiation lets the adapter and the switch agree on the highest shared speed, which is 100 Mbps or 1 Gbps on most home networks.

Enable the Onboard LAN in the BIOS

Enabling the onboard LAN controller in the BIOS restores an Ethernet adapter that is missing from Windows because the firmware disabled it. The setting sits in the onboard devices section of the BIOS or UEFI.

1. Restart the computer and press the BIOS key, often Delete, F2, or F10, during boot.
2. Open the Advanced or Onboard Devices section.
3. Find the Onboard LAN, Integrated NIC, or LAN Controller setting.
4. Set the value to Enabled.
5. Save and exit, then confirm the Ethernet adapter appears in Device Manager.

A computer with no Ethernet adapter listed in Device Manager and no driver fault points to a disabled onboard LAN in the BIOS. A USB-to-Ethernet adapter restores a wired link when the onboard controller has physically failed.

Ethernet Not Working Symptoms and Likely Causes

Key Takeaways

• Check the cable and link lights first. A dark link light at both ports points to a cable, port, or adapter fault.
• Swap the cable and port to isolate the fault. A working link on a second device proves the cable is good.
• Enable a greyed-out adapter. A disabled adapter in Network Connections shows no connection at all.
• Reinstall a faulty driver. A yellow warning icon in Device Manager confirms a corrupt Ethernet driver.
• Check the BIOS when the adapter is missing. A disabled onboard LAN hides the wired adapter from Windows.

Last Thoughts on Ethernet Not Working

Ethernet not working is resolved by working from the cable outward to the BIOS and checking the link after each step. Inspecting the cable and link lights, swapping the cable and port, enabling the adapter, and reinstalling the driver fix most wired faults without new hardware. When no connection forms over either medium, the steps to fix no internet connection cover a full outage, and a wireless alternative is covered in the guide to fix Wi-Fi that keeps disconnecting.

The hub page listing common PC problems connects every troubleshooting topic. Readers who want to understand the addresses that DHCP assigns to a wired adapter can review the explanation of what an IP address is.