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Home » Fix Connection Failed Error 651 in Windows 11 and 10 (2026 Guide)

Fix Connection Failed Error 651 in Windows 11 and 10 (2026 Guide)

The Connection Failed — Error 651 is a common Windows networking problem. It usually appears when you try to connect to the internet using a broadband (PPPoE) connection. When Error 651 appears, Windows can’t establish a proper connection between your computer and the internet, so you’re unable to browse online. The root cause of error 651 can vary, including software conflicts, driver issues, network misconfigurations, or problems with your ISP or modem/router. Here are several troubleshooting methods to resolve this error and establish an internet connection on your PC.

How to Fix Connection Failed Error 651

You mostly see this error when you try to connect to or share your broadband connection with one or more devices. Several factors can trigger error 651, including network misconfigurations, problems with your ISP, or your modem/router.

  • Incorrect Network Configuration – Misconfigured network settings can prevent the connection from being established.
  • Corrupt or Outdated Network Drivers – Faulty drivers can cause connectivity issues, making it essential to keep them updated.
  • Conflicts with Network Services – Background services, such as Windows updates, security software, or VPNs, may interfere with internet access.
  • Damaged System Files – Corrupt Windows system files may prevent the PPPoE connection from working properly.
  • ISP or Modem Issues – Sometimes, the problem is caused by an issue on the ISP’s end, a faulty modem, or a bad internet line.

Use this quick flow to decide what to try next:

  1. Is only this PC affected?
    • Yes → Continue with the steps above (software/driver fixes).
    • No, all devices offline → Likely ISP/modem issue → Contact ISP.
  2. After restart and cable checks, does Error 651 still appear?
    • Yes → Run Network troubleshooters and recreate PPPoE.
  3. Still failing?
    • Update / reinstall network drivers.
    • Test with IPv6 disabled.
  4. Still no luck?
    • Reset TCP/IP and Winsock.
    • Temporarily disable VPN/security software.
  5. If it still doesn’t work → Very likely ISP or modem/router problem → Contact ISP or replace hardware.

Restart Your Modem and Router

Power cycling your modem and router is the simplest and often most effective way to resolve temporary network glitches. Restarting refreshes the connection between your ISP and your device.

  • Turn off your modem and router.
  • Unplug them from the power source and wait for 5 minutes to clear network cache.
  • Plug them back in and turn them on.
  • Allow the devices to fully reboot and try reconnecting to the internet.

Check Physical Cables and ISP Status

Before changing Windows settings, make sure the basics are fine.

  1. Check the DSL/fiber cable going into your modem — make sure it’s firmly connected.
  2. Check the Ethernet cable between your PC and router/modem (if you’re on wired).
  3. If possible, connect another device (laptop or phone via Wi‑Fi) to see if it can access the internet.
  4. Visit your ISP’s status page on another connection (mobile data) or call them to check for outages.

If other devices also can’t connect, the problem may be with your ISP or modem, not your PC.

Run the Windows Network Troubleshooter

Windows has built‑in troubleshooters that can automatically detect and repair common network problems.

On Windows 11

  1. Press Win + I to open Settings.
  2. Go to System > Troubleshoot > Other troubleshooters.
  3. Run these troubleshooters one by one:
    • Internet Connections
    • Network Adapter
  4. Follow the on‑screen instructions and apply any suggested fixes.
  5. Restart your PC if asked, then test the connection.

On Windows 10

  1. Press Win + I to open Settings.
  2. Go to Update & Security > Troubleshoot.
  3. Click Additional troubleshooters.
  4. Run:
    • Internet Connections
    • Network Adapter
  5. Follow the prompts, apply fixes, and restart your PC.

Network Troubleshooter windows 10
If Error 651 still appears, move on.

Disable and Re-Enable the Network Adapter

If your network adapter is experiencing issues, disabling and re-enabling it can help reset the connection. This method forces Windows to reload the network adapter, eliminating any minor software glitches affecting connectivity.

  • Press Win + X and select Device Manager.
  • Expand Network adapters to view the list of installed network devices.
  • Right-click your active network adapter and select Disable device.
  • Wait for a few seconds, then right-click it again and select Enable device.
  • Try connecting to the internet again to see if the problem is resolved.

Create a New Dial-Up (PPPoE) Connection

If your broadband connection settings are corrupted, creating a new PPPoE connection ensures that your internet connection is properly configured with the correct credentials.

Windows 11

  1. Press Win + I to open Settings.
  2. Go to Network & internet > Dial‑up.
  3. Click Set up a new connection.
  4. Select Connect to the Internet, then click Next.
  5. Choose Broadband (PPPoE).
  6. Enter your ISP username and password.
  7. Give the connection a recognizable name.
  8. Click Connect and see if the error is gone.

Windows 10

  1. Open the Control Panel (press Win + R, type control, and press Enter).
  2. Go to Network and Sharing Center.
  3. Click Set up a new connection or network.
  4. Select Connect to the Internet > Broadband (PPPoE).
  5. Enter your ISP username and password.
  6. Name the connection and click Connect.

If the new connection dials successfully, you can delete the old one.

Update or Reinstall the Network Driver

Outdated or corrupt network drivers can cause connection failures, including error 651. Updating or reinstalling them ensures smooth connectivity. Update or reinstall the network driver, ensure you are using the latest driver version, and prevent compatibility issues that may trigger error 651.

Update the driver via Device Manager

  1. Press Win + X and select Device Manager.
  2. Expand Network adapters.
  3. Right‑click your active adapter (for example, Realtek PCIe GBE, Intel(R) Ethernet).
  4. Click Update driver.
  5. Select Search automatically for drivers.
  6. Let Windows search and install any available updates.
  7. Restart your PC and test the connection.

Reinstall the driver (clean)

If the problem continues:

  1. In Device Manager, right‑click your network adapter.
  2. Click Uninstall device.
  3. If you see Delete the driver software for this device, you can tick it to force a clean reinstall.
  4. Click Uninstall.
  5. Restart your PC — Windows will attempt to automatically reinstall the driver.

uninstall Network adapter driver

Install the latest driver from the manufacturer

For the best results:

  1. Visit your motherboard / laptop / network card manufacturer’s website.
  2. Download the latest Windows 10/11 network driver for your exact model.
  3. Run the installer and follow the on‑screen instructions.
  4. Restart your PC and test the PPPoE connection again.

Disable IPv6 on Your Internet Connection

Some networks experience compatibility issues with IPv6, which may result in connection errors.

  1. Press Win + R, type ncpa.cpl, and press Enter.
    (This opens the Network Connections window in both Windows 10 and 11.)
  2. Right‑click your active connection (Ethernet or Wi‑Fi) and choose Properties.
  3. In the list, find Internet Protocol Version 6 (TCP/IPv6).
  4. Uncheck it.
  5. Click OK to save changes.
  6. Restart your PC and try connecting again.

If this doesn’t help, you can enable IPv6 again by re‑checking the box.

disable IPv6

Reset TCP/IP Stack and Winsock

If your network configuration is badly corrupted, resetting TCP/IP and Winsock can fix deep‑level issues that cause Error 651.

Important: This will reset some custom network settings (like manual IPs or DNS). Note them down first if you’ve set them.

  1. Press Start, type cmd.
  2. Right‑click Command Prompt and choose Run as administrator.
    (Or in Windows 11, you can use Windows Terminal (Admin).)
  3. In the command window, run these commands one by one, pressing Enter after each:
netsh int ip reset
netsh winsock reset
ipconfig /flushdns
  1. Close the Command Prompt window.
  2. Restart your computer.
  3. Try your PPPoE connection again.

Temporarily Disable VPN and Security Software

VPN clients, firewalls, and some antivirus suites can interfere with PPPoE connections.

  1. Disconnect from any VPN you’re using.
  2. Temporarily disable third‑party antivirus or firewall software.
  3. Try connecting again.

If the connection works with them disabled, review their network settings or contact the software provider for a permanent fix. Don’t leave security software disabled permanently.

Contact Your ISP or Replace Faulty Hardware

If none of the software fixes work, the issue may be outside your computer.

  • Contact your Internet Service Provider (ISP) and:
    • Ask if there are outages in your area.
    • Confirm your PPPoE username and password.
    • Ask them to test your line and reset your connection from their end.
  • If your modem/router is very old or frequently loses connection, ask about a replacement.

FAQ: Connection Failed Error 651

1. What is Error 651 in Windows?
Error 651 is a Windows network error that usually appears when a PPPoE broadband connection fails. It means Windows couldn’t establish a proper link between your PC and your ISP.

2. Does Error 651 only affect Windows 10?
No. Error 651 can appear in both Windows 10 and Windows 11, because both use similar networking components and PPPoE handling.

3. Is Error 651 caused by my ISP or my computer?
It can be either:

  • If other devices and connections work fine, the problem is likely your PC (drivers, settings, PPPoE profile).
  • If all devices fail to connect, it’s more likely an ISP, modem, or line issue.

4. Will resetting TCP/IP or Winsock delete my files?
No. Those resets only affect network configuration, not your personal files. You may need to re‑enter custom IP, DNS, or VPN settings afterward.

5. How do I know if my network driver is the problem?
Common signs:

  • Frequent disconnects or no network after Windows updates
  • Error 651 even after recreating PPPoE and running troubleshooters
  • Network adapter showing warning icons in Device Manager

Updating or reinstalling the driver (as shown above) is usually enough.

6. Can IPv6 cause Error 651?
In some older or misconfigured networks, IPv6 can cause compatibility issues. Disabling IPv6 on your adapter is a safe test. If nothing changes, you can turn it back on.

Robeg

I am Robeg founder of this blog. My qualification. completed Bachelor of Arts (BA) and Microsoft Certified Professional (MCP). With a strong background in computer applications love write articles on Microsoft Windows (11, 10, etc.) Cybersecurity, WordPress and more.

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