Why is my Ethernet not working?

The most common causes of Ethernet not working are: a bad or loose cable, a wrong cable type (old Cat5 instead of Cat5e/Cat6), a failed router/switch port, a disabled network adapter, incorrect IP configuration, or an outdated driver. Start by swapping the cable, then check if the adapter is enabled in your network settings.

How do I fix Ethernet connected but no internet?

Run ipconfig (Windows) or ifconfig (Mac/Linux) to check if you received an IP address. A 169.254.x.x address means DHCP failed — the cable is connected but no IP was assigned. Try releasing and renewing: ipconfig /release then ipconfig /renew on Windows. Also try power cycling the router. If you get a valid 192.168.x.x IP but still no internet, the issue is with the router's internet connection, not the Ethernet itself.

Ethernet Not Working — Complete Fix Guide

Quick Diagnosis — Check These First

Symptom	Most Likely Cause	Fix
No link light on router/PC port	Bad cable, wrong port, or adapter disabled	Replace cable, check adapter is enabled
Link light on, but 169.254.x.x IP	DHCP failure — cable connected but no IP assigned	ipconfig /release + /renew; power cycle router
Link light on, valid IP, no internet	Router internet issue (not Ethernet itself)	Check router WAN connection; reboot modem
Very slow speeds (10–100 Mbps on Gigabit)	Old cable, duplex mismatch, or wrong cable category	Replace with Cat5e or Cat6; check duplex settings
Works on one computer, not another	Driver issue or adapter problem on the failing machine	Update/reinstall network adapter driver
Works on WiFi but not Ethernet	Router LAN port failed, or cable issue	Try a different router port; swap cable

Step 1 — Check the Physical Connection

Unplug and firmly re-insert both ends of the Ethernet cable — the RJ45 connector should click into place. A partially seated connector can cause intermittent or no connectivity. Check the link lights:

On the router's LAN port: should show a green or amber light when cable is connected
On your computer's Ethernet port: similar indicator light
No light at either end = bad cable, wrong port, or adapter disabled

Try a different cable. Ethernet cables are the most common point of failure and a cheap replacement cable ($5–10) eliminates the variable instantly. If you are using a cable longer than 100 meters (328 feet), that exceeds the Ethernet spec — signal degradation is expected.

Step 2 — Check Which Cable Category You Have

Category	Max Speed	Max Frequency	Recommended?
Cat5	100 Mbps	100 MHz	No — too old for Gigabit
Cat5e	1 Gbps	100 MHz	Yes — minimum for Gigabit
Cat6	1–10 Gbps	250 MHz	Yes — good for most home use
Cat6A	10 Gbps	500 MHz	Yes — for 10G or long runs
Cat8	25–40 Gbps	2000 MHz	Overkill for home; short runs only

Look at the cable jacket — the category is printed along the cable. Cat5 cables will cap at 100 Mbps. If you have Gigabit internet and Cat5, the cable is your bottleneck.

Step 3 — Windows Fixes

Enable the adapter (if disabled): Right-click the Start button → Device Manager → Network Adapters → right-click your Ethernet adapter → Enable Device. If it shows a yellow warning triangle, there is a driver problem.

Release and renew IP (for 169.254.x.x or no connectivity):

# Open Command Prompt as Administrator:
ipconfig /release
ipconfig /flushdns
ipconfig /renew
netsh winsock reset

Restart network stack:

netsh int ip reset
# Reboot after running this

Check and set adapter duplex: Go to Device Manager → Network Adapters → right-click Ethernet adapter → Properties → Advanced tab → Speed & Duplex. Set to "Auto Negotiation" (or match what the router port is set to). A duplex mismatch (half vs full duplex) causes poor performance and packet loss even when the cable is fine.

Update/reinstall driver: Device Manager → Network Adapters → right-click Ethernet adapter → Update Driver. If that does not help, download the latest driver directly from your laptop/motherboard manufacturer's website (Intel, Realtek, and Broadcom are the most common Ethernet chip makers).

Step 4 — Mac Fixes

Check adapter recognition: System Information (Apple menu → About This Mac → System Report → Network) shows all detected network interfaces. If Ethernet does not appear here, macOS is not detecting the adapter at all — driver or hardware issue.

Renew IP: System Settings → Network → select Ethernet → Details → TCP/IP → click Renew DHCP Lease.

Create new network location: If the adapter is stuck with bad settings, System Settings → Network → Location dropdown → Edit Locations → add a new location. This creates a fresh network configuration profile.

USB-C Ethernet adapter: If using a USB-C or Thunderbolt Ethernet adapter, try a different USB-C port or hub. Some USB-C hubs have Ethernet adapters that require specific macOS drivers — check the adapter manufacturer's website.

Step 5 — Check the Router LAN Port

If you have a second device available, plug it into the same router port — if it also does not work, the router port may have failed. Try a different LAN port on the router. Router LAN ports can fail individually due to power surges or physical stress. Most consumer routers have 4 LAN ports — if one fails, the others usually still work.

Step 6 — Check for IP Address Conflict

If two devices on your network have the same IP, one or both will have connectivity problems. Run ipconfig (Windows) or ifconfig (Mac) to see your current IP. If you see a 169.254.x.x "APIPA" address, DHCP failed. If you see a valid 192.168.x.x but still no internet, ping your router: ping 192.168.1.1. If the router does not respond, the issue is between your PC and the router. If it does respond, the issue is the router's internet connection — check by loading the router admin page.

Ethernet Adapter Hardware Issues

If none of the above resolves the issue and the adapter is not detected at all (not in Device Manager or System Information), the Ethernet port may be physically damaged. Common causes: liquid damage, static discharge, or physical impact. A USB 3.0 to Gigabit Ethernet adapter ($15–25) is an affordable way to add a working Ethernet port if the built-in one is dead. These use standard Realtek or ASIX chips with well-supported drivers on all major operating systems.