FIX: Windows 10 VPN error 789 connection failed

Milan Stanojevic
by Milan Stanojevic
Windows & Software Expert
Milan has been enthusiastic about PCs ever since his childhood days, and this led him to take interest in all PC-related technologies. Before joining WindowsReport, he worked as a front-end web developer. Read more
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  • VPN error 789 appears when a Windows 10 system isn't configured properly and it is connected to a VPN using the L2TP protocol.
  • This error can be fixed with a quick network adapter reset from Device Manager.
  • IPSec configuration should be changed as well as a fallback solution so tweak the services as shown in our guide.
  • You should also consider changing your virtual private network less prone to errors.
FIX: Windows 10 VPN error 789 connection failed due to security issues

If you’re using a VPN, you can get prompted with the Windows 10 VPN error 789 that states the following message:

The L2TP connection attempt failed because the security layer encountered a processing error during initial negotiations with the remote computer

This error pops up when your system is not properly set up to connect to an L2TP server, thus the connection attempt fails even before you establish a connection with the server.

It is also linked to the incorrect configuration of your operating system like Windows 10 in this case. This generic error is thrown when the IPSec negotiation fails for the L2TP/IPSec connections.

Other possible causes include:

  • L2TP based VPN client (or VPN server) is behind NAT
  • Wrong certificate or pre-shared key is set on the VPN server or client
  • A machine certificate or trusted root machine certificate is not present on the VPN server
  • Machine Certificate on VPN Server does not have Server Authentication as the EKU

Before trying any of these solutions, ensure that L2TP and IPSec pass-through options are enabled from your router.

If you configured your VPN service manually, then make sure you use the preshared key 12345678. Here are solutions you can use to fix Windows 10 VPN error 789 on your computer.

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How do I fix Windows 10 VPN error 789?

  1. Reset network adapter
  2. Check the certificate
  3. Re-enable IPSec on your computer

1. Reset network adapter

  1. Right-click Start and select Device Manager.device manager
  2. Identify your network adapter and right-click on it then select Uninstall device.
  3. Click OK.
  4. Restart your computer. The device will reinstall and should reset it to default settings.

Refreshing the network adapter driver can make this problem go away quickly so make sure you try it out by performing the steps above.

2. Check the certificate

It is very important to ensure the correct certificate is used both on the client and the server-side.

In case that the two don’t match, you won’t be able to use the virtual private network. You might need to renew the certificate with your provider.

If you are using a Pre Shared Key (PSK), ensure that the same PSK is configured on the client-side, and the VPN server machine.

3. Re-enable IPSec on your computer

  1. Press the Windows key + R keyboard shortcut to start Run.
  2. Type services.msc and press Enter or click OK.disable windows error reporting service
  3. Find the IKE and AuthIP IPSec Keying Modules service.
  4. Find IPSec Policy Agent.
  5. Check the status for both services. If it says started click to restart. If the started option is disabled, enable it
  6. Double click on each of the two.
  7. Select Startup type.
  8. Change it to Automatic.
  9. Save the changes.
  10. Restart your VPN service.

Once you have done all the steps above carefully, the VPN should work smoothly as the protocol settings have been reset to default.

If, however, it doesn’t work, you have to manually set the encryption method both for the server and the client-side, in order for them to be compatible.

In case you have a user-specific issue on your computer yet you still get the L2TP connection attempt failed error, you can also contact the customer care or tech support team for your specific VPN provider.

Of course, you can also change your software completely. Just check our list comprising the best VPNs for Windows 10 and pick the one that suits your needs.

Do let us know if any of these solutions fixed the Windows 10 VPN error 789 by leaving a comment in the section below.

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Frequently Asked Questions

  • The ports you need to open are 500 and 4500 for UDP. Check out the complete guide on unblocking L2TP for other ports and more.

  • L2TP stands for Layer 2 Tunneling Protocol and is considered better than PPTP. It secures the traffic passing by it in an IPsec tunnel. If you have issues with it, we have an excellent guide on how to fix L2TP problems.

  • By resetting the network adapter or setting the firewall to allow traffic through port 500. More details in this excellent guide.

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