What is VPN Error 789 and How to Fix It

In this article we explain what VPN Error 789 is and how to fix it.

What is VPN Error 789?

If you are a frequent computer user, you probably have come across VPN Error 789. This is a common problem and error that occurs on single-user computers.

The error occurs when the PC user attempts to use a VPN solution while utilizing the Microsoft Windows functionality. The VPN Error 789 is common in Windows 7 and Windows 10 Operating Systems. As the error is common, one might be prompted to ask why one would go through the struggle, and process of solving the error.

Why use a VPN?

A VPN is a Virtual Private Network. As the name suggests, it makes it possible for one to have online privacy. The VPN achieves privacy and anonymity by creating a private network, operating on the Public Internet Connectivity. This means that despite being on the Wide Web, one is virtually on a scaled-down network. 

As technology advances, different VPNs have been designed. They come with different functionalities, depending on the desired results. Some are free, while others are paid. In most cases, the efficiency of the VPN depends on its type, design, and nature of availability to the public.

It can be argued that it is probably without a doubt that a paid-for VPN is more effective and efficient compared to a free one. As mentioned, some VPNs are free, with some limitations where others come with a small fee giving the full suite of features.

 

Different users attest to the challenge of getting error as they use the above-mentioned VPNs. Different reasons lead to these errors and will be mentioned in the sections that follow. The common error is VPN Error 789.

When using a personal computer, the error reads, “VPN Error 789: The L2TP Connection Attempt Failed.”

This is one error that should not send shivers down your spine, as I will be proving the best solutions for the error. The solutions are effective and work in a minute of troubleshooting. Even though solving it is an easy process, it is important to understand some of the causes of Error 789. 

Possible Causes of VPN Error 789 in Windows 7/10

As previously mentioned, Error 789 occurs when a computer user tries to initiate a connection to a Layer 2 Tunnelling Protocol (L2TP). If the error occurs while trying to establish a connection, it should be obvious that there is a problem with the computer system, or the VPN itself.

On one side, it could be an indication that your computer is wrongly configured to connect to the VPN. On the other side, it could be an indication that the VPN being used is not functioning correctly, and therefore, rejecting connections from the PC.

When the computer is configured wrongly, any attempts that are meant to connect to the VPN are dropped before they reach any server for instance.

• Existence of NAT in the Network

This is the first cause of Error 789. It occurs in a scenario where the PC or the VPN client or PC server is logically behind a Network Address Translation. If the correcting NAT is not implemented, then requests are blocked, and network addresses are not resolved as they should be translated.

• Machine Certificate Error

When the Machine or PC certificate or that of the root machine is not visible in the network or does not have the right authentication protocols, a machine error occurs, and this could lead to Error 789. It is important to note that when a machine certificate is not visible, it means that it is not available in the network.

• Missing Registry keys

When Registry keys are missing, then it will mean that your machine will keep losing its connection to the VPN, prompting the occurrence of Error 789. When Registry keys are missing, it is possible to key them in using the Registry Editor.

• Disabled IPsec Keying Modules and Policy Agents

When these two entities are disabled, or stopped, the VPN does not function. This is because they are necessary for the functioning of the self-hosted VPNs. Therefore, when the two entities are not available for utilization, Error 789 occurs.

Fixing VPN Error 789

The solutions to the error are easy if the right troubleshooting instructions are followed. In the Information technology world, and Computer networking, most of the solutions are found through the restarting of computer systems.

This is the first solution, and to some people, it might sound like a non-solution, but it has been found to work. Therefore, when faced with VPN Error 789, the first thing you will want to do is to restart your computer and try to connect to the VPN again, if the error does not appear, then there you have solved the problem.

If the problem persists even after the restart, the following troubleshooting guidelines should help you solve the problem. It is important to note that one does not have to try all the solutions, as the first one could be enough to settle your headache.

Solution-1: Resetting Network Adaptors

In the Computing World, Error 789 can occur as a result of an unstable network. This can arise as a result of computer Network Adaptors. When the network adaptors are not working correctly, the computer’s initiated communication with the VPN will not flow smoothly. This causes interruptions that will lead to VPN Error 789.

To ensure that the problem is not with the network adaptors, what one needs to do is to readjust the network adaptor. This is done by the device manager of the computer.

Once your there, all you need to do is to uninstall the drivers, and reinstall them. Make sure that the drivers you reinstall are compatible with your computer.

Guide to Uninstall and Reinstall Network Drivers on your Computer

1. Right, Click on the Start Menu. Then select Device Manager. Or Press Windows key Plus R. This opens the run command > In the Pop-Up window, type devmgmt.msc and press ENTER.
2. A User Account Control Prompt might appear. Click YES to proceed.
3. After the above steps, The Device Management Screen will appear. Using the Scroll up and Down keys, Scroll down to Network Adaptor. Click it to extend the drop-down Menu.
4. Right Click on Network Adaptor and select Uninstall from the options presented. 
5. Click OK and wait for the initiated process to Complete.
6. Once completed, restart your computer to reinstall the Uninstalled Network Adaptor.

Once completed, see if the VPN Error 789 still occurs. If the problem still exists, move on to Solution-2 below.

Solution-2: Certificate Verification

When there is a misconfiguration of certificates or the pre-shared key from the client or server, VPN error 789 might occur. To ensure this does not happen, confirm proper configuration and also that the right certificate is being utilized in both the client and server sides. If a pre-shared key is being used, ensure that the correct key is utilized on both sides as well.

Solution-3: UDPE Encapsulation Registry Key

This is the solution needed when the server and client are situated behind NAT. in this case, you must build construct the AssumeUDPEncapsulationContextOnSendRule Registry Key. 

Getting Started with AssumeUDPEncapsulationContextOnSendRule Registry Key

1. Press Windows Key + R. This will open Run Dialog Box. Type regedit and press ENTER. This will open the Registry Editor.
2. Once the Registry Editor Appears, use the following path as shown below;

HKEY_LOCAL MACHINE > SYSTEM > CurrentControlSet > Services > PolicyAgent

• Once at Policy Agent as directed in the above path, Right-click on the space and select New-DWORD (32-Bit).
• Name the now created DWORD as AssumeUDPEncapsulationContextOnSendRule. Press Enter to create it as the new Registry value.
• Double Click on the created value and set its value to 2 and the base of the same to hexadecimal. Then click OK.

Now Restart Your System to check if VPN ERROR 789 is resolved.

Solution-4: Enabling IPsec and Policy Agent Services

In most cases, VPN Error 789 occurs as a result of disabled IPsec and Policy Agent Services. The guide below directs you on how to enable IPsec and Policy Agent Services.

Guide on Enabling IPsec and Policy Agent Services

1. Press Windows Button + R. This will open RUN Dialog Box. Type services.msc and press ENTER.
2. The Services screen will appear. Scroll down to look for IKE and AuthIP IPsec Keying Modules. Double click on each to see if they are enabled or disabled.

• On the General tab of the IPsec and Policy Agent Services, Enable Automatic Start-Up Type. 
• Restart your PC and check if the VPN Error 789 is resolved.

Conclusion

Resolving VPN Error 789 can be done by following the four methods outlined above. It is important to note that troubleshooting can be stopped once the problem is solved. For instance, if solution-1 works, you do not have to go all the way to solution-4.

A similar error that you might face is the VPN error 809, here’s how you can fix this issue.