Built-In Windows L2TP VPN Is Not Working

Question

I am getting an error when trying to use the Built-In Windows L2TP VPN.

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

I have used the Built-In Windows VPN daily without any issue until today (1/12/2022).
This issue is happening on my machine as well as a coworkers machine. I looked in my windows update history and it looks like the two following updates were applied to my machine overnight (Sometime early in the morning on 1/12/2022)

1. https://support.microsoft.com/en-us/topic/january-11-2022-kb5009543-os-builds-19042-1466-19043-1466-and-19044-1466-b763552f-73bd-435a-b220-fc3e0bc9765b
2. https://support.microsoft.com/en-us/topic/january-11-2022-kb5008876-cumulative-update-for-net-framework-3-5-and-4-8-for-windows-10-version-20h2-windows-server-version-20h2-windows-10-version-21h1-and-windows-10-version-21h2-bb0dbbd8-b24f-4e92-95d2-465e6be223fc

The issue seems to only happen with windows users that are using the Build-In L2TP VPN. I have a coworker that uses a Mac and he can connect to our VPN with the L2TP Protocol just fine. After hearing that he had no issues on a Mac I downloaded a third party VPN client and was able to connect to the VPN. So I have a workaround for now, but I would much prefer to use the Built-In VPN. Any help in getting this issue resolved would be much appreciated. Thank you!

Here is the info for the windows version my machine is running
Edition Windows 10 Pro
Version 20H2
Installed on ‎5/‎12/‎2021
OS build 19042.1466
Experience Windows Feature Experience Pack 120.2212.3920.0

Answer 1

KB5009543 (Jan 11) now acknowledges the VPN issue ( https://support.microsoft.com/en-gb/topic/january-11-2022-kb5009543-os-builds-19042-1466-19043-1466-and-19044-1466-b763552f-73bd-435a-b220-fc3e0bc9765b ) and offers out-of-band KB5010793 (Jan 17) ( https://support.microsoft.com/en-gb/topic/january-17-2022-kb5010793-os-builds-19042-1469-19043-1469-and-19044-1469-out-of-band-f2d4f178-5b36-49cb-a6fd-4bf9857574f9 ) as a fix.

Answer 2

You're awesome! Thanks for the share, Vinny!

Answer 3

Hello Vinny,

Thank you for your question and reaching out.

I can understand you are facing issue with connecting built-in VPN.

It looks to be know issue with recent updates as other users has also reported this similar issue as yours, I will suggest you to please check if this KB5009543 and KB5009566 is installed on your VM or PC , and then Uninstall it and try to connect to VPN.

https://techcommunity.microsoft.com/t5/report-an-issue/windows-11-update-kb5009566-inhibits-vpn-connection/m-p/3057844

https://learn.microsoft.com/en-us/answers/questions/691993/can39t-connect-to-any-vpn-after-today39s-windows-u.html

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Answer 4

Sadly this issue is not resolved yet across all versions. I'm using Windows 11 Enterprise build 22538.10.10 and the L2TP client is still not working. Can Microsoft provide a link to a 3rd-party software client that will be compatible whilst we wait (who knows how long) for them to restore functionality?

Answer 5

and now the fix won't install so still no working vpn. and that is on a fresh install of windows 10.
2022-01 Cumulative Update for Windows 10 Version 21H2 for x64-based Systems (KB5010793)

I tried every solution I could find the only one remaining is to do yet another fresh install