Ethernet Not Working: How to Tell If It’s the Cable, the Port or the Computer

A wired connection is supposed to be the reliable one, so it is confusing when it stops working. The cause is almost always in one of four places: the cable, the port on the router, the router itself, or the network adapter and its settings on the computer. A few swaps tell you which one it is, and then the fix is quick.

What Exactly Is Wrong?

The message on your computer already narrows it down:

If Wi-Fi on the same computer also has no internet, the problem is not the cable at all — see Wi-Fi connected but no internet and check the router lights first.

Step 1: Find Where the Problem Is

Do these three swaps, one at a time:

1. Another cable. If a different cable works, the first one is faulty.
2. Another port on the router. If a different LAN port works, the port is the problem.
3. Another device on the same cable. If a laptop or console works with that cable and port, the problem is on your computer.

Also look at the lights next to the port, on the router and on the computer. On most devices a steady light means a link and blinking means traffic. No light at all on either end means no physical connection.

Step 2: Check the Cable

Look along the whole cable for kinks, crushed spots under furniture or doors, and cuts. Check the plugs: the small plastic clip should click into place, and a broken clip lets the plug slip out just enough to lose the link.

Plug it in again firmly at both ends. Avoid running a cable through a wall coupler or old wall socket while testing; connect the computer directly to the router if you can.

If the link only reaches 100 Mbps, one of the wire pairs is probably damaged. Gigabit Ethernet needs all four pairs in the cable, while 100 Mbps needs only two, so a cable with one broken pair often still “works” at the lower speed. For new cables, Cat 5e is enough for 1 Gbps and Cat 6 is a good choice for faster connections; see Ethernet vs Wi-Fi for cable types.

Step 3: Check the Router Side

Use a LAN port, not the Internet port. Microsoft’s troubleshooting guide points this out first: the computer must go into one of the numbered LAN ports. The Internet or WAN port, often a different color, is for the cable from the modem.

Restart the modem and router. Unplug both, wait at least 30 seconds, plug in the modem, wait until its lights stop blinking, then plug in the router. This renews the connection to your provider and clears a router that has stopped handing out addresses.

Check that the router itself has internet. If no device in the home gets online, the problem is the router or the provider, not the cable.

Step 4: Fix It on Windows

If the cable and the router are fine, the computer is the last suspect. Microsoft and Dell list these steps, in this order.

Check the status. Open Settings → Network & internet. The Ethernet connection should show Connected. If it shows an error, open it for details.

Run the network troubleshooter. On Windows 11 it runs in the Get Help app and fixes common problems automatically.

Reset the network stack. Open Command Prompt as administrator and run these commands one by one:

netsh winsock reset
netsh int ip reset
ipconfig /release
ipconfig /renew
ipconfig /flushdns

Then restart the computer. This fixes most cases of “Unidentified network”, which usually means the computer did not get an address from the router. If the address starts with 169.254, the router’s DHCP did not answer; restarting the router and running ipconfig /renew again usually helps. Our local IP address tool shows what address the computer has.

Reinstall the network driver. In Device Manager, expand Network adapters, right-click the Ethernet adapter and choose Uninstall device, then restart; Windows reinstalls the driver. Microsoft recommends downloading the latest driver from the computer maker first, so you have it if Windows does not find one. This step is especially worth trying if Ethernet stopped working after an update.

Turn off power saving for the adapter. Dell suggests unchecking Allow the computer to turn off this device to save power on the adapter’s Power Management tab. It helps with connections that drop.

Check that the adapter is enabled. If the Ethernet adapter does not appear in Device Manager at all, it may be disabled in the BIOS or UEFI settings, as Dell notes for its computers.

Use network reset as the last step. Settings → Network & internet → Advanced network settings → Network reset removes and reinstalls all network adapters and returns their settings to defaults. You may need to set up VPN software again afterwards.

On a Mac

Open System Settings → Network and select Ethernet (or the name of your USB-C adapter). A green dot and Connected mean the link is up. If it shows a self-assigned IP address, the router did not answer: open Details → TCP/IP and click Renew DHCP Lease. If no Ethernet entry appears with a USB-C or Thunderbolt adapter, unplug the adapter, plug it in directly rather than through a hub, and check whether it needs a driver from its maker.

Ethernet Works but Is Slow

Check the link speed. On Windows it is shown under Settings → Network & internet → Ethernet as Link speed; on a Mac, under the Ethernet hardware details. If a gigabit router and computer link at 100 Mbps, replace the cable first, then try another port. If the link speed is right but the internet is slow, the cable is not the issue; see why is my Wi-Fi so slow for testing your connection.