Ethernet should be the most reliable connection, but when it stops working, here’s how to fix it.

Quick Diagnosis

Check Physical Connections

1. Check cable at both ends - firmly plugged in?
2. Look at port lights:
   • Green/amber light = connected
   • No light = no connection
3. Try a different cable - cables do fail
4. Try a different port on router/switch

Check Network Status

1. Click network icon in taskbar
2. Should show “Connected” for Ethernet
3. If “Not connected” or “No internet,” continue below

Cable and Hardware Checks

Test the Cable

1. Try a known-good Ethernet cable
2. Try your cable on another device
3. Check for visible damage (bent pins, cuts)

Test the Port

1. Try a different port on your router
2. Try connecting directly to modem (temporarily)
3. Check if other devices work on that port

Check Network Adapter Lights

On the Ethernet port:

• No lights: Cable issue or adapter disabled/dead
• Lights on, no internet: Software/configuration issue

Enable Ethernet Adapter

Check if Disabled

1. Press Windows + R, type ncpa.cpl
2. Right-click Ethernet adapter
3. If it says “Enable,” click it

Device Manager Check

1. Open Device Manager
2. Expand Network adapters
3. Find Ethernet adapter (usually has “Ethernet,” “LAN,” or “GbE”)
4. If gray arrow, right-click > Enable device
5. If yellow warning, driver issue

Driver Fixes

Update Ethernet Driver

1. Device Manager > Network adapters
2. Right-click Ethernet adapter
3. Update driver > Search automatically
4. Restart if updated

Reinstall Ethernet Driver

1. Device Manager > right-click Ethernet adapter
2. Uninstall device
3. Check “Delete driver software” if shown
4. Restart
5. Windows reinstalls driver

Download Driver from Manufacturer

For best results:

1. Identify your adapter in Device Manager
2. Visit manufacturer website:
   • Intel: intel.com
   • Realtek: realtek.com
   • Or your motherboard/laptop manufacturer
3. Download and install latest driver

Network Settings Fixes

Reset Network Settings

Complete reset of all network configuration:

1. Settings > Network & internet
2. Advanced network settings
3. Network reset
4. Click Reset now
5. Restart and test

Reset Network Stack

1. Open Command Prompt as Administrator
2. Run these commands:

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

3. Restart computer

Check IP Configuration

1. Command Prompt: ipconfig
2. Look at Ethernet adapter section
3. Should have valid IP address (not 169.254.x.x)
4. If 169.254.x.x - not getting IP from router

Set IP Automatically

1. Press Windows + R, type ncpa.cpl
2. Right-click Ethernet > Properties
3. Double-click Internet Protocol Version 4
4. Select Obtain IP address automatically
5. Select Obtain DNS server automatically
6. OK and test

Service Fixes

Check DHCP Client Service

1. Press Windows + R, type services.msc
2. Find DHCP Client
3. Ensure it’s running and set to Automatic
4. If not, start it

Check Network Services

Ensure these are running:

• DHCP Client
• DNS Client
• Network Connections
• Network Location Awareness

Run Troubleshooters

Network Adapter Troubleshooter

1. Settings > System > Troubleshoot
2. Other troubleshooters
3. Run Network Adapter
4. Select Ethernet
5. Apply fixes

Internet Connections Troubleshooter

1. Same location
2. Run Internet Connections
3. Follow prompts

Advanced Fixes

Disable Energy Efficient Ethernet

Power saving can cause issues:

1. Device Manager > Ethernet adapter > Properties
2. Advanced tab
3. Find Energy Efficient Ethernet or Green Ethernet
4. Set to Disabled

Disable Power Management

1. Ethernet adapter Properties
2. Power Management tab
3. Uncheck “Allow computer to turn off this device”

Set Speed and Duplex

Auto-negotiation sometimes fails:

1. Ethernet adapter Properties > Advanced
2. Find Speed & Duplex
3. Try 100 Mbps Full Duplex instead of Auto
4. If works, try 1.0 Gbps Full Duplex

Disable IPv6

Sometimes causes connectivity issues:

1. Ethernet Properties (ncpa.cpl)
2. Uncheck Internet Protocol Version 6
3. Click OK and test

Disable Large Send Offload

Can cause connection issues:

1. Ethernet adapter Properties > Advanced
2. Find Large Send Offload (v1 and v2)
3. Set to Disabled

Router/Modem Fixes

Restart Network Equipment

Order matters:

1. Turn off computer
2. Unplug modem (if separate)
3. Unplug router
4. Wait 30 seconds
5. Plug in modem, wait 2 minutes
6. Plug in router, wait 2 minutes
7. Turn on computer

Check Router Settings

1. Log into router admin
2. Check DHCP settings are enabled
3. Ensure Ethernet ports aren’t disabled
4. Check for firmware updates

Test Without Router

To isolate the issue:

1. Connect computer directly to modem
2. Restart modem
3. If internet works, router is the issue

Check for Hardware Failure

Signs of Failed Ethernet Port

• No lights ever, with any cable
• Device Manager shows errors
• Works after restart, then fails

Test with USB Ethernet Adapter

1. Get a USB to Ethernet adapter ($15-25)
2. Plug in and let Windows install driver
3. Connect Ethernet cable to adapter
4. If it works, internal port may be dead

BIOS Check

Ethernet might be disabled in BIOS:

1. Restart and enter BIOS
2. Look for:
   • Onboard Devices
   • Integrated Peripherals
   • LAN/Ethernet
3. Ensure Ethernet is Enabled
4. Save and exit

Ethernet Still Not Working? Our Dallas technicians diagnose wired network issues quickly. We can identify cable, hardware, or configuration problems.

Prevention Tips

1. Use quality Ethernet cables - Cat6 or better
2. Don’t bend cables sharply
3. Protect ports from dust
4. Keep drivers updated
5. Use surge protector for router/modem

If WiFi trouble goes beyond this one error, our complete WiFi troubleshooting guide covers diagnosis from router to device, room by room.