VPN Error 691: Causes and Solutions

Are you annoyed by VPN Error 691 when connecting to a virtual private network? This error can be very frustrating, but fear not! In this blog post, we'll discuss what VPN Error 691 is, why it happens, and how to fix it. Read on to learn more.

What Is VPN Error 691?

VPN error 691 is an authentication error that occurs when a user attempts to connect to a virtual private network (VPN) and fails to be authenticated by the server. This error is most commonly caused by an incorrect username or password or an authentication protocol mismatch between the client and the server. Other causes of this error include problems with the remote server, network connectivity issues, or an incorrect VPN client configuration.

Method for Resolving Error 691 in Windows 10

So far, we've learned the reasons that could lead to Error 691. In this section, we provide you with easy-to-follow solutions to fix them. Let's check them out together.

Method 1: Checking your Username and Password

Most of the problems are caused by the wrong password and username. So, always ensure you're using the correct ones and check them twice.

Additionally, consider resetting your password and username; if you have trouble recalling them, try entering them again.

Method 2: Remove the .local extension from the Domain name

Have you ever noticed the field for entering a domain name while entering your password and username? Remove the .local extension if it's added with the domain name and try to log in to VPN.

Method 3: Leave out the domain name blanket

You can also clear out the domain name if the above method doesn't work out for you and try to log in again.

Method 4: Enable Microsoft CHAP Version 2

To fix error 691, you might need to change the protocol from VPN properties on your computer. Here is how to do it:

1. Open the Windows menu by pressing Win + X on your keyboard.
2. Select the Network Connection option.
3. Right-click on the VPN connection and open Properties.
4. In the new window, open the Security tab and check the Allow these protocols.
5. Select Microsoft CHAP Version 2 (MS-CHAP v2) and click Ok to save changes.

Method 5: Uncheck "include Windows Logon domain" Box

Another way to fix Error 691 is disabling the Include Windows Logon Domain option. Let's see how to do it step by step:

1. Press Win + X buttons on your keyboard, then select Network Connection.
2. Right-click the VPN Network in the new window, then click the Properties option.
3. Open the Options tab; under the Dialing options section, uncheck the Include Windows Logan domain.
4. Save the changes by clicking on OK.

Method 6: Change the LAN Manager Parameters

Based on most users' experience, one of the ways that you can easily fix Error 691 is by changing the LAN Manager Parameters. Follow the steps below:

1. Open the Group Policy Editor by pressing the Win + R buttons, type gpedit.msc, and click OK to continue.
2. In the Group Policy Editor, navigate to the left panel and select the Security Options folder.
3. Double-click the Network security: Lan Manager authentication level option in the right panel.
4. In the VPN Connection Properties, select Send LM & NTLM responses option and save the changes by clicking Ok.
5. Return to the Group Policy Editor table, then double-click the Network Security: Minimum Session Security for NTLM SSP option on the right panel. 
6. In the new window, check the Require NTLMv2 session security option, uncheck the Require 128-bit encryption option, and save changes by clicking Ok.
7. Restart your computer and check if Error 691 was fixed.

Method 7: Update the Network Driver

Always make your that the Network Driver is updated. Because if you don't, you will face various problems, including VPN issues. To update your driver, follow the steps below.

1. Press Win + X keys on your keyboard.
2. Select the Device manager option from the menu.
3. Expand the Network adapter device in the menu
4. Right-click on the Wi-Fi receiver driver.
5. Select the Update Driver Software option.

Click the Search automatically for the updated driver software option. Now Windows will search your computer and the internet for the latest diver software for your device.

Complete the update process, restart your computer, and check whether it worked.

Method 8: Use the "resphone command" for your VPN connection

There is another helpful command to fix VPN Error 691 in windows 10. Follow the steps below:

1. Press Win + X to open the Windows Menu, then select the Command Prompt (Admin) option
2. Now type the following command, then press Enter

Syntax: rasphone -d VPNname

Remember to replace the VPN name with your computer's connection name. You can find the name of your connection by pressing Win + I and clicking the Network connection.

Method 9: Make sure that only one VPN is active at the time

If you have more than one VPN on your computer, always ensure that just one is running on your PC at the time. Because VPNs generally support only one connection at a time.

Sometimes VPNs could start automatically; in this case, ensure that only necessary Windows services start as you turn on your PC. Plus, it can be easily done by booting your system.

Method 10: Re-register the VPN connection

You can delete the VPN connection and add it again, which might help resolve Error 691.

Take the following step:

1. Press the Win + I buttons to open the Setting app on your computer.
2. Select the Network and Internet option.
3. Navigate to the left panel and click The VPN option
4. Go to the right panel and click on the Remove option.
5. Click on Add a VPN connection and add the new connection
6. Restart your computer and try out the new VPN connection.

Conclusion

• VPN error 691 is an authentication error that occurs when a user fails to be authenticated by the VPN server.
• Common causes of error 691 are an incorrect username or password or an authentication protocol mismatch between the client and the server.
• You can try removing the .local extension from the Domain name, enabling Microsoft CHAP Version 2, and changing the LAN Manager Parameters to fix error 691.

FAQ

What is VPN error 691?

VPN Error 691 is an error that occurs when a user attempts to connect to a VPN and fails to be authenticated by the server.

What causes VPN error 691?

VPN error 691 is typically caused by incorrect login information or a network problem. 

Is there a way to fix error 691?

Yes. You can check the login information to ensure it is correct, reset the network connection, or reinstall the VPN software. 

Does VPN error 691 always indicate a problem with my login information?

Not necessarily. It could also indicate an issue with the VPN server or software or a problem with the network.

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