- Overview
- Terms and Definitions
- Steps
- Step 1 — Check Physical Link Lights and Cable
- Step 2 — Confirm Adapter Detection
- Step 3 — Restart or Reinstall Network Drivers
- Step 4 — Verify IP Configuration
- Step 5 — Disable Power Saving Features
- Step 6 — Check Router and Switch Ports
- Step 7 — Reset Network Stack and DNS
- Step 8 — Reset Firmware Controllers
- Step 9 — Check Event Logs
- Verification
- Conclusion
Overview #
If your laptop or desktop’s wired internet connection suddenly stops working—or the Ethernet port doesn’t light up—the issue is usually driver-related, cable-related, or power-related, not a failed motherboard.
This guide walks through the exact steps to verify the LAN adapter, restore link lights, and re-enable reliable wired connectivity on both Windows and macOS.
What you’ll learn
- How to confirm that the Ethernet adapter is active and detected
- How to reinstall or roll back network drivers
- How to test cables, jacks, and link lights
- How to reset network stack and firmware settings
Estimated time: 15–30 minutes
Skill level: Intermediate
Terms and Definitions #
| Term | Meaning |
|---|---|
| LAN (Local Area Network) | Wired connection between your device and router/switch |
| RJ-45 jack | Standard Ethernet port on most laptops and desktops |
| Link lights | Small LEDs near the Ethernet jack indicating physical connectivity |
| DHCP | Service that automatically assigns IP addresses on your network |
| MAC address | Unique hardware ID for your network adapter |
Steps #
Step 1 — Check Physical Link Lights and Cable #
- Look for green or amber LEDs on the Ethernet jack.
- Steady light: physical link detected
- Blinking light: data activity
- No light: cable or port issue
- Try a different cable or different router port.
- If you’re using a USB-to-Ethernet adapter, move it to another USB port and observe if lights appear.
- If possible, test the same cable with another computer.
If link lights remain off, continue to driver and power checks.
Step 2 — Confirm Adapter Detection #
Windows PowerShell
Get-NetAdapter | Where-Object {$_.Name -like "*Ethernet*"} | Select-Object Name, Status, LinkSpeed, MacAddress
If the adapter is Disabled:
Enable-NetAdapter -Name "Ethernet"
macOS Terminal
networksetup -listallhardwareports
Look for “Hardware Port: Ethernet” and note the Device (e.g., en0).
Check interface status:
ifconfig en0
If it doesn’t show “status: active,” the cable isn’t linked or the driver isn’t active.
Step 3 — Restart or Reinstall Network Drivers #
Windows
- Open Device Manager → Network adapters.
- Right-click your Ethernet adapter (Realtek, Intel, Broadcom, etc.) → Disable device, then Enable device.
- If still inactive, choose Uninstall device, then Scan for hardware changes.
- Optionally, download the latest driver from your laptop manufacturer or NIC vendor.
PowerShell
Get-NetAdapter | Disable-NetAdapter -Confirm:$false
Get-NetAdapter | Enable-NetAdapter -Confirm:$false
macOS
Ethernet drivers are built-in. If the port isn’t active, delete and re-add the interface:
sudo ifconfig en0 down
sudo ifconfig en0 up
Step 4 — Verify IP Configuration #
Windows
ipconfig /all
Check:
- IPv4 address is valid (not
169.254.x.x) - Default gateway is listed
If you see a 169.254 address, renew DHCP:
ipconfig /release
ipconfig /renew
macOS
ifconfig en0
If no IP is assigned, renew:
sudo ipconfig set en0 DHCP
Step 5 — Disable Power Saving Features #
Windows
- Open Device Manager → Network adapters → [Your Ethernet Adapter] → Properties.
- Go to the Power Management tab.
- Uncheck:
“Allow the computer to turn off this device to save power.” - Click OK.
macOS
Disable energy-saving network options:
sudo pmset -a womp 0
(womp = “Wake on Magic Packet”) — sometimes triggers network instability after sleep.
Step 6 — Check Router and Switch Ports #
- Try another Ethernet port on your router or switch.
- Power-cycle your router: unplug for 30 seconds, plug back in.
- If using a managed switch, ensure the port isn’t administratively disabled.
- Connect directly from laptop → modem (bypass router) to isolate the problem.
Step 7 — Reset Network Stack and DNS #
Windows
netsh winsock reset
netsh int ip reset
ipconfig /flushdns
Restart afterward to apply.
macOS
sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder
Flushes DNS and resets cache.
Step 8 — Reset Firmware Controllers #
Windows (EC Reset)
- Shut down your laptop.
- Disconnect charger and battery (if removable).
- Hold Power for 15 seconds.
- Reconnect and start up.
macOS (SMC Reset)
- Shut down.
- Hold Shift + Control + Option + Power for 10 seconds.
- Release all keys and start the Mac.
These resets reinitialize hardware controllers that handle I/O power—including Ethernet.
Step 9 — Check Event Logs #
Windows PowerShell
Get-WinEvent -LogName System | Where-Object {$_.Message -like "*Ethernet*"} | Select TimeCreated, Message -First 15
Look for:
- “Link Down” / “Media Disconnected”
- “Driver failed to start”
macOS
log show --predicate 'eventMessage CONTAINS "Ethernet"' --last 2h
Confirms whether macOS is detecting link attempts or driver restarts.
Verification #
| Check | Command | Expected Result |
|---|---|---|
| Physical link | Visual | Link LEDs on and blinking |
| Adapter status | Get-NetAdapter / ifconfig en0 | Status = Up or Active |
| IP address | ipconfig / ifconfig | Valid DHCP address |
| Connection | ping 8.8.8.8 | Replies received |
Conclusion #
A non-functional Ethernet port is often a matter of drivers, power management, or cable failure, not a dead motherboard.
By checking physical link lights, reinstalling drivers, disabling power saving, and resetting your network stack, you can restore stable wired connectivity quickly.
If link lights stay dark across multiple cables and systems, the LAN controller or port itself may have failed and require professional repair.
