Fix: The modem has reported an error with an Error Code 651 in Windows 11, 10

Several Windows users have recently complained that when they attempted to connect their modem for internet access on their PC, it generated an error that said The modem (or other connecting device) has reported a problem with error code 651 and does not allow to connect to the system.


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This issue might have been caused by a fault with the system or the modem, an outdated network card driver, the autotuning option not being disabled, and so on.

Keeping all of these things in mind, this post will show you a variety of fixes that may be able to resolve this issue and allow users to connect the modem to the system without trouble.

If you are experiencing a similar problem, please continue reading to learn more.

Before that, you can try these workarounds given below –

  1. Reboot the system a few times and check if the issue got fixed.
  2. Try connecting the modem to another system to check if the problem is with the system.
  3. If not, try connecting another modem (different connection) to see if the modem is having any issues.
  4. Check for cable whether it is loose or broken/damaged.
  5. Try restarting the system in safe mode with networking and see if it works!

Fix 1 – Disable the Auto Tuning feature

To increase network performance, Windows added the auto-tuning function, which monitors network latency, bandwidth, and other parameters. Enabling this functionality may also result in the above-mentioned problem.

So we suggest the users disable the auto-tuning feature on their system. Let us see how this can be done using the simple steps given below.

Step 1: Press the Windows + X keys together to see the context menu of the Start button.

Step 2: Then, tap on the R key on your keyboard to open the Run command box.

Step 3: Type cmd in the textbox of the Run window and press CTRL + SHIFT + ENTER keys together to open the command prompt as admin.

NOTE: Also accept the UAC prompt by clicking Yes to proceed.

 

7 Run Cmd Optimized

 

Step 4: Copy and paste the below-given command in the command prompt window that just opened and hit Enter key to execute it.

Netsh interface tcp set global autotuning=disabled

 

Disable Auto Tuning Feature 11zon

 

Step 5: This will disable the auto-tuning feature on your system.


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Step 6: Once done, close the command prompt window.


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Now check if the internet connection could be established by connecting the modem to your system.

Fix 2 – Reset TCP/IP on the Windows system

TCP and IP are both in charge of establishing a reliable connection between computers that can readily interact with one another. TCP permits data packets to be sent from one device to another by utilising the IP address, which contains device information.

This sort of problem is common when TCP/IP settings are modified. So, follow the procedures below to reset the TCP/IP.

Step 1: Press the Windows and R keys together on your keyboard which opens the run box.

Step 2: Next type cmd in the Run box and tap on CTRL + SHIFT + ENTER keys together to open the elevated command prompt.

Step 3: Click Yes on the User Access Control Prompt to continue.

 

Run Cmd Min

 

Step 4: Enter the following line in the command prompt and execute it by pressing Enter key.

netsh int ip reset reset.log

Step 5: This will reset the TCP/IP on your system.

 

Reset Tcp Ip 11zon

 

Step 6: Once it is done, close the command prompt and reboot your system and then check if the problem is solved.

 

Fix 3 – Disable the Internet Protocol Version 6 IPv6

Try disabling the IPv6 on your system from the network connections page for the ethernet adapter and check if the problem could be fixed.

Follow the steps given below on how to do it.

Step 1: Press the Windows and R keys together to open the Run command box.

Step 2: Type ncpa.cpl in the Run box and press Enter key to open the network connections page.

 

Run Ncpa Min

 

Step 3: Right-click on the Ethernet adapter and click Properties from the context menu as shown below.

 

Ethernet Properties 11zon

 

Step 4: Once the Ethernet Properties window opens, uncheck the Internet Protocol Version 6 (IPv6) checkbox and click OK.

 

Internet Protocol Version 6 Uncheck 11zon

 

Step 5: This will disable the IPv6 on your system for Ethernet.

Now try to establish the connection to your system and check if that worked.

 

Fix 4 – Run Network Adapter Troubleshooter

There is a troubleshooter inbuilt into the windows system called Network adapter, which tries to detect and fix the network-related issues.

Let us see how to run the network adapter troubleshooter on the system.

Step 1: Open the Run box by pressing the Windows and R keys simultaneously.

Step 2: Type control.exe /name Microsoft.Troubleshooting in the run box and press Enter key to open the Troubleshoot page directly.

 

Run Command Control.exe Name Microsoft.troubleshooting Enter

 

Step 3: Select Other troubleshooters options by clicking on it as shown below.

 

Other Troubleshooters Min

 

Step 4: Scroll down the page and perform the Network Adapter troubleshoot by clicking Run as shown in the below image.

 

Run Network Adapter Troubleshooter 11zon

 

Step 5: It will start detecting the problems related to the network adapter and follow the onscreen instructions to fix the issue if any are found.

Step 6: Once done, close the window and check if the issue is resolved.

 

Fix 5 – Update the Network Driver via Device Manager

The outdated network driver sometimes causes issues that are not easily detected while troubleshooting. So we recommend users update the network driver on your Windows system via device manager. Let’s see how to update it using the steps below.

Step 1: Press the Windows + X keys together to view the context menu of the Start button and hit the M key to open the Device Manager.

Step 2: Double-click on the Network adapters options to expand it.

Step 3: This contains all the network adapters available on the system.

Step 4: Right-click on the Ethernet WAN Miniport and click Update driver from the context menu as shown in the below screenshot.


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Update Network Wan Miniport Driver 11zon

 

Step 5: Perform the onscreen instructions to complete the update process.

Step 6: Once done, close the device manager.

 

Fix 6 – Try re-registering the raspppoe.sys file

The file called raspppoe.sys is located in the folder system32 on your windows system and this is responsible for the better communication between your system and other connected devices. So let us re-register the raspppoe.sys file, which will repair it if there is any problem with it.

Step 1: Press the Windows key and type cmd.

Step 2: Then, right-click on the Command Prompt app and select Run as administrator from the list as shown below.

Step 3: Click Yes to accept any UAC prompt that pops up to proceed.

 

Command Prompt Run As Admin 11zon

 

Step 4: Once the command prompt opens, type regsvr32 raspppoe.sys and hit the Enter key.

 

Reregister Raspppoe File 11zon (1)

 

Step 5: This will re-register the raspppoe.sys file.

Step 6: Next, close the command prompt window and restart the system.

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