- 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 and a certificate check. IPSec configuration should be changed as well as a fallback solution.
- If you are interested in VPN protocols, check out our encryption section on the website to learn more.
- Visit the VPN How-to Guides for articles that instruct you on how to get the most out of your VPN.
If you’re using a VPN, and get prompted with the Windows 10 VPN error 789 that states:
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
Here are solutions you can use to fix Windows 10 VPN error 789 on your computer.
How do I fix Windows 10 VPN error 789?
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.
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1. Reset network adapter
- Right-click Start and select Device Manager
- Find Network adapters and click to expand the list
- Identify your network adapter and right-click on it then select Uninstall
- Click OK
- Restart your computer. The device will reinstall and should reset it to default settings
If this doesn’t fix Windows 10 VPN error 789, try the next solution.
2. Check the certificate
Ensure the correct certificate is used both on the client and the server-side. In case Pre Shared Key (PSK) is used, ensure that the same PSK is configured on the client-side, and the VPN server machine.
3. Re-enable IPSec on your computer
- Right-click Start and select Run
- Type services.msc
- Find IKE and AuthIP IPSec Keying Modules
- Find IPSec Policy Agent
- Check the status. If it says started click to restart. If the started option is disabled, enable it
- Double click on each of the two
- Select Startup type
- Change it to Automatic
- Save the changes
- 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 Windows 10 VPN error 789 after trying any of the above solutions, you can also contact the customer care or tech support team for your specific VPN provider and share the details for further assistance.
Do let us know if any of these solutions fixed the Windows 10 VPN error 789 by leaving a comment in the section below.
FAQ: Learn more about VPN error 789 in Windows 10
- What ports need to be open for L2TP VPN?
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.
- How does L2TP VPN Work?
L2TP stands for Layer 2 Tunneling Protocol and is considered better than PPTP. It secures the traffic passing through it, in an IPsec tunnel. The traffic itself is not encrypted.
- How do I fix Error 789 L2TP?
By resetting the network adapter or setting the firewall to allow traffic through port 500. More details in this article.
Editor’s Note: This post was originally published in March 2018 and has been since revamped and updated in May 2020 for freshness, accuracy, and comprehensiveness.Editor's Note: This article was originally published in March 2018 and was revamped and updated in September 2020 for freshness, accuracy, and comprehensiveness.