Bothered by Connection Failed with Error 651? Fix It Now

What Is Connection Failed with Error 651?

You may encounter different kinds of network connection issues when using your computer. The connection failed with error 651 is a common issue.

The error 651 can happen on Windows 10, Windows 8/8.1, and Windows 7. It always happens when you want to connect your computer to the internet. When this issue happens, you will receive an error window with the alert saying: Error 651: The modem (or other connecting devices) has reported an error.

This modem error 651 indicates that the internet connection is failed or the existing network connection has been terminated.

Reasons for Modem Error 651

Why connection failure error 651 occurs? The possible causes are various. Both hardware and software issues can lead to this issue. We have searched for this issue on the internet and colleted some information.

The already known reasons for error 651 include a .SYS file is placed in a wrong location, the modem is set up incorrectly, the registry files are corrupt, an IP address is conflicted with another, and driver issues.

Focusing on these reasons, we collect some solutions to help you get rid of this connection error 651. If you don’t know the real cause of this error, you can try these solutions one by one until finding the proper one.

# Fix 1: Check for Loose Cables

You need to guarantee that all the power and connection cables are plugged in properly to your computer, modem, router, and wall. This is the easiest tip but the most effective one.

# Fix 2: Reregister the Raspppoe.sys File

The raspppoe.sys file is a Windows RAS PPPoE mini-port driver file. It enables your computer to communicate with your computer hardware or connected devices. If there is something wrong with this file, you will get the connection failed with error 651.

You can re-register that file to fix the issue:

1. Go to Start > Search.
2. Type cmd into the search box.
3. Right-click the first result and select Run as administrator.
4. Input the following command and press Enter:

regsvr32 raspppoe.sys

When the process ends, you need to restart your computer to see whether the error 651 disappears.

# Fix 3: Restart the Router/Modem

The connection failure error 651 can also be caused by a faulty router/modem. You can just restart the router/modem to see whether the issue can be solved.

#Fix 4: Update the Drivers for the Modem

You can update the drivers for modem using Device Manager. You can also go to the manufacturer’s official site to download the latest version of the drivers and then install them on your computer.

#Fix 5: Reset TCP/IP or Internet Protocol

Some users say that they solved the issue by resetting TCP/IP to its factory settings using NetShell. You can also use this method to have a try.

#Fix 6: Run the Network Troubleshooter

The network troubleshooter is specially used to solve some network issues. You can use it to have a try.

You can open Run, type msdt.exe /id NetworkDiagnosticsNetworkAdapter and press Enter to open the Network Adapter Troubleshooter. Then, you can run it to fix your problem.

#Fix 7: Disable the Auto-Tuning Feature

The Windows Auto-Tuning feature can improve the performance for programs that receive TCP data over a network. When you receive this connection error 651, you can disable it to have a try:

1. Run Command Prompt as administrator.
2. Type the following command and press Enter to disable the Auto-Tuning feature:

netsh interface tcp set global autotuning=disabled

We hope the connection failed with error 651 issue should be solved after using these methods.