Windows 11 VPN Connection - The L2TP connection attempt failed because the security layer

Question

Windows 11 VPN Connection - The L2TP connection attempt failed because the security layer

Tanima Sonar 0

Hi,

I am trying to connect VPN via WireGaurd that used to work before. I can see that my wireguard is activated and it's sending and receiving handshakes but when I try to connect to vpn I'm getting this error:

Windows 11 VPN Connection Error: The L2TP connection attempt failed because the security layer encountered a processing error during initial negotiations with the remote computer.

I'm using Windows 11 Enterprise
Version 25H2

* αmαndα * 0 Reputation points

2026-08-26T23:37:12.2333333+00:00

We've started seeing this error in our environment in the last couple of days as well. Would any recent W11 patches or updates have possibly caused this?

1 answer

Your answer

* αmαndα * 0 Reputation points

2026-08-26T23:37:12.2333333+00:00

We've started seeing this error in our environment in the last couple of days as well. Would any recent W11 patches or updates have possibly caused this?

Answer 1

Hi @Tanima Sonar ,

Thank you for contacting to Microsoft Community.

You could try these steps below to fix the issue related L2TP:

Open Command Prompt as Administrator:

Copy and paste the following commands

REG ADD HKLM\SYSTEM\CurrentControlSet\Services\PolicyAgent /v AssumeUDPEncapsulationContextOnSendRule /t REG_DWORD /d 0x2 /f

REG ADD HKLM\SYSTEM\CurrentControlSet\Services\RasMan\Parameters /v ProhibitIpSec /t REG_DWORD /d 0x0 /f

Restart Your Computer:

After executing the commands, restart your computer to apply the changes.

If the issue continues, additional troubleshooting may be necessary, including reviewing network settings or removing recent updates.

If you found this answer helpful, please click "Accept Answer" to support our community and others.

Thank you again for your patience and support!

Dustin Tran