How to Troubleshoot VPN Error 789 on Windows PC

  • Windows users connect and install a VPN service on their Windows 10 computers to optimize privacy and security features when connecting to the Internet.
  • When you connect to a server using the L2TP protocol, the connection processing ends with error 789, followed by error 791.
  • It’s possible that the client you’re using isn’t configured to connect to the VPN server.

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The L2tp Connection Failed Because The Security Layer Encountered

An error occurred during initial negotiations with the remote computer caused one of my customers to be unable to connect to VPN today.

L2tp Connection Attempt Failed Windows 10

There are times when you may encounter an error with the L2TP connection attempt because it encountered a processing error in Windows 10 or 11. L2TP is a well-known VPN that utilizes the Layer 2 tunneling protocol, bypassing security restrictions in certain areas. As a result of this issue, a VPN error 789 is reported, which indicates a conflict between the security layer and the remote VPN server when attempting to connect.

An error 789 was returned when I setup a VPN connection from Windows 7 to a Mac OS X VPN server: 

If you want to connect to the Internet with privacy and security features, you should use a VPN service installed on your Windows 10 computer. VPNs have many other benefits. However, not everything goes smoothly with VPNs. There are network errors that can occur regardless of your operating system.

There has been an error with the VPN connection job as of 24th January GMT:

Our topic today will be VPN 789 in Windows 10. This error is a common VPN error that Windows users experience on a regular basis. It is possible that the client you’re using is not configured to connect to the L2TP VPN server when you connect to it using the L2TP protocol. It shows the following error message when you connect to a server using the L2TP protocol:

There was an error in the negotiation with the remote computer that resulted in the L2TP connection attempt being failed.

What causes the VPN 789 error?

Windows 10 Vpn L2tp Connection Attempt Failed

“Can’t connect to VPN” is causing users trouble. In an initial negotiation with the remote computer, the security layer encountered a processing error, resulting in a failed L2TP connection attempt. The issue mostly affects Windows VPN connections with Ubiquiti Client-to-Site VPNs, SonicWalls, Cisco Merakis, and WatchGuard firewalls through the built-in Windows VPN client.

A computer user experiences Error 789 when connecting to a Layer 2 Tunnelling Protocol (L2TP) connection, as previously mentioned. A problem with the computer system or VPN itself should be obvious if the error occurs while trying to establish a connection.

Missing encapsulation registry key: If you are experiencing frequent disconnects and failed connection attempts related to your VPN, it is probably due to a missing registry key called AssumeUDumeUDPEncapsulationContextOnSendRule. In this case, you can solve the problem by creating and configuring this registry key manually using the registry editor.

The server and client sides both need to use the correct certificate. The virtual private network will not function if the certificate is not valid. Besides that, if you are using a PSK, make sure you configure it the same way on the client and server sides.

Network mismatch: It turns out that network mismatch can also be the cause of this particular error message. In most cases, the problem is caused by a network card that is stuck in an undefined state, so that a VPN connection cannot be established. If this scenario applies, you can solve the problem by resetting the network adapter and having the operating system reinstall the network driver.

Using this solution, you must be running Windows 7 or Windows Vista.

IPsec key modules and the policy agent are disabled: These two services are absolutely essential if you’re using a VPN on your own hosting. Without them, you can’t connect. If this scenario applies, you can solve the problem by going to the Services screen and making sure that both services are enabled and the Startup Type is set to Automatic.

Interference from a third-party firewall: Another possible cause of this error is an overly secure firewall blocking certain ports that are actively used by your VPN connection. In this case, you can solve this problem by setting exceptions or removing the third-party firewall.

How to solve the VPN 789 error?

Updated: February 2024

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The network adapter needs to be reset

This problem can be quickly solved by updating the network adapter drivers. Here are the steps you need to follow to do that.

  1. Choose Device Manager from the menu that appears when you right-click Start.
  2. Choose Uninstall Device from the right-click menu of the network adapter you want to uninstall.
  3. Click OK.
  4. Your computer will be rebooted, and the device will be reinstalled.

Re-enabling IPSec on your PC

You should now have no problems using the VPN if you follow the steps below carefully.

  1. For a quick start, press Windows and R at the same time.
  2. Click OK after entering services.MSC.
  3. Find the AuthIP IPSec Keying Modules and the IKE service.
  4. The IPSec policy agent can be found by searching for it.
  5. Both services should be shown as Started; if so, restart them.
  6. The Started option needs to be enabled if it isn’t already.
  7. Each service should be double-clicked.
  8. Types of startups can be chosen.
  9. Automatic should be selected.
  10. Changes should be saved.
  11. Your VPN service needs to be restarted.

RECOMMENATION: Click here for help with Windows errors.

Frequently Asked Questions

  1. Restart the VPN network adapter.
  2. Verify the certificate.
  3. Turn on the IPsec service again.

  1. Press Win + R to bring up the Run dialog box.
  2. Right-click on the VPN connection and select Properties.
  3. In the VPN properties, go to the Security tab and turn on the Allow these protocols option.
  4. Enable the Microsoft-CHAP Version 2 option and click OK.

This error may occur if the VPN server is not properly connected to the network, if the network is temporarily down or if the server or network is overloaded with traffic. The error also occurs if the VPN client has incorrect configuration settings.

  1. A possible solution for this common type of VPN error is the built-in diagnostic with recovery provided by Windows.
  2. Stop and start the Remote Access Connection Manager (rasman) service.
  3. Simply reboot the system and then connect to the VPN.

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Mark Ginter is a tech blogger with a passion for all things gadgets and gizmos. A self-proclaimed "geek", Mark has been blogging about technology for over 15 years. His blog,, covers a wide range of topics including new product releases, industry news, and tips and tricks for getting the most out of your devices. If you're looking for someone who can keep you up-to-date with all the latest tech news and developments, then be sure to follow him over at Microsoft.