The Broadband 651 modem reported an error, the underlying causes of which involve multiple levels, including drivers, system services, network configuration, and hardware wiring. The repair process should follow the principle of “software first, hardware second; simple first, complex third”: first restart the device and reset the protocol stack, then check services and drivers, and finally troubleshoot hardware and carrier-side issues.
I. What is Error 651?
Error 651 is a common connection failure code when dialing up broadband PPPoE in Windows systems. It indicates “Connection failed, error 651. The modem (or other connection device) reported an error.” When a user dials up to access the internet via broadband, the system is unable to establish communication with the ISP’s server, resulting in a complete network outage.
II. Quick Repair: Basic Troubleshooting
When you encounter error 651, don’t rush to reinstall the system. First, complete the following basic operations, and many problems can be solved on the spot:
1. Restart the optical modem/router: Unplug the power and wait 1-2 minutes before powering it back on to allow the device to fully reinitialize.
2. Restart your computer: This will rule out connection problems caused by temporary system processes freezing.
3. Re-plug the network cable: Make sure both ends of the network cable (computer network port and optical modem LAN port) are firmly plugged in, and observe whether the network port indicator light is flashing normally.
4. Redial: Wait for the optical modem indicator light to stabilize (usually the PON light is constantly on) before connecting to broadband.
5. Verify account and password: Confirm that the broadband account and password are correct, paying attention to capitalization and special characters.
If error 651 persists after the above steps, proceed to the next in-depth troubleshooting step.
III. In-depth investigation and repair
Repair Option 1: Reset the network protocol stack and Winsock
Winsock is the Windows network programming interface, responsible for data transmission between applications and the network. Resetting Winsock can clear configuration corruption caused by software conflicts or abnormal shutdowns.
1. Open Command Prompt (CMD) as an administrator.
2. Enter the following commands sequentially, pressing Enter after each line:
netsh winsock reset
netsh int ip reset
ipconfig /flushdns
netsh interface tcp set global autotuninglevel=disabled
3. Restart your computer after all operations are complete.
4. Recreate the broadband connection after restarting and test dialing.
▎Remediation Direction Two: Check the Status of Critical System Services
PPPoE dialing relies on multiple system background services. If a service is disabled or stops abnormally, it will directly trigger error 651.
1. Press Win + R, type services.msc to open the Services Manager.
2. Check the following services one by one to ensure that their “Startup type” is “Automatic” and their status is “Running”:
Remote Access Connection Manager
Remote Access Auto Connection Manager
Telephony (telephone service)
Windows Event Log
Secure Socket Tunneling Protocol Service
3. If the service is not running, right-click and select “Start”, and set the startup type to “Automatic” in “Properties”.
4. After making the changes, restart your computer and try dialing again.
Repair Option 3: Recreate the broadband connection
The original dial-up connection configuration file may be corrupted. Recreating it can rule out configuration-level issues.
1. Open “Settings” → “Network & Internet” → “Dial-up” → Delete the existing broadband connection.
2. Click “Set up a new connection” → Select “Connect to the Internet” → “Broadband (PPPoE)”.
3. Re-enter the broadband account and password provided by the operator.
4. Check “Remember this password” and click “Connect” to test if it works normally.
▎Repair Option 4: Update or reinstall the network card driver
Network card driver malfunction is a frequent cause of error 651, especially after system updates or the installation of Ghost versions of the system, which can easily lead to driver compatibility issues.
Manual repair steps:
1. Right-click “This PC” → “Manage” → “Device Manager”.
2. Expand “Network Adapters” and check if the network card device has a yellow exclamation mark.
3. Right-click the network adapter → “Uninstall device”, and check “Delete the driver software for this device”.
4. Restart your computer; Windows will automatically install the basic network card driver.
5. Redial test.
Use Driver Life to automatically repair (temporary internet connection required):
If you can download the driver via USB tethering on your phone, connecting to another Wi-Fi network, or borrowing another device, it is recommended to use ” Driver Life ” to resolve driver issues.
97% positive reviews
Downloads: 5,305,1501. Download Driver Life Network Card Edition (which comes with a universal network card driver) on a device with internet access, copy it to the computer with the problem, and install it.
2. Open Driver Life and click “Diagnose Now”. The software will automatically detect if there are any abnormalities in the network card driver.
3. If you find that the network card driver version is too old, the file is corrupted, or there is a conflict with other components, click “Full Repair”.
4. Driver Life will automatically match the official stable version of the driver for the current network card model and complete the download and installation.
5. After installation, restart your computer and reconnect to broadband.
▎Fixed Option 5: Modify Network Card Duplex Mode
Some older optical modems or carrier equipment are incompatible with the network card’s auto-negotiation mode; manually specifying the speed can resolve this issue.
1. Open Device Manager → Expand “Network adapters” → Right-click the network adapter and select “Properties”.
2. Switch to the “Advanced” tab.
3. Locate “Speed & Duplex” or “Speed & Duplex”.
4. Change the value from “Auto Negotiation” to “100 Mbps Full Duplex” or “10 Mbps Full Duplex”.
5. Click OK and redial to test.
▎Remediation Direction Six: Investigate Hardware and Carrier-Side Issues
If the above software-level repairs are ineffective, hardware and wiring issues need to be investigated:
1. Test by replacing the network cable: Oxidation or internal breakage of the network cable connector can cause abnormal signal transmission.
2. Test by changing the network port: If the optical modem has multiple LAN ports, try changing to other network ports.
3. Test other devices: Connect your phone or another computer to the same network cable and dial up to confirm whether the problem is only affecting one computer.
4. Contact your internet service provider: Call your internet service provider’s customer service hotline to confirm that your broadband account is in good standing, has no outstanding fees, and is not bound to a MAC address. At the same time, ask customer service to refresh the port or check the data center’s lines.
