Ethernet connection cutting out after hours on Windows 11

Symptoms

Ethernet works normally for several hours, then disconnects
Reconnecting the cable restores internet temporarily
Disconnects become more frequent over time
Restarting the computer resets the problem
Replacing cables and restarting the router does not help

Why This Happens

Windows 11 aggressively manages network power and efficiency. Over extended uptime, some Ethernet drivers gradually enter an unstable state due to power-saving transitions, link renegotiation, or thermal stress. This behavior is most commonly seen with: - Realtek Ethernet adapters - Intel integrated Ethernet controllers - Generic drivers installed via Windows Update The adapter remains “connected,” but packet transmission degrades until the link effectively fails.

Step-by-Step Troubleshooting

Step 1: Disable Adapter Power Saving

Open Device Manager.
Expand Network adapters.
Right-click your Ethernet adapter and select Properties.
Open the Power Management tab.
Uncheck “Allow the computer to turn off this device to save power.”
Click OK and restart.

Step 2: Disable Energy Efficient Ethernet

Energy Efficient Ethernet dynamically lowers power usage but can destabilize the connection. - Open adapter Properties. - Go to the Advanced tab. - Disable Energy Efficient Ethernet or similar options.

Step 3: Install Manufacturer Drivers

Avoid Windows Update drivers. - Identify the adapter model. - Download drivers from the motherboard or chipset manufacturer. - Install and reboot.

Step 4: Check Thermal Conditions

After several hours of operation: - Check airflow around the system. - Clean dust from vents. - Ensure the system is not enclosed tightly.

Step 5: Test with a USB Ethernet Adapter

Using a USB Ethernet adapter helps isolate motherboard hardware issues.

When This Topic Is Limited

Once power management and drivers are addressed, there are few remaining branches. Persistent issues may indicate failing motherboard hardware.

Summary

Ethernet dropouts after long uptime on Windows 11 are nearly always caused by driver or power-management behavior. Disabling efficiency features and using proper drivers resolves most cases.