L2TP /IPSec issue on Windows

RouterOS General
1

Hi

Hoping someone can assist or point me in the right direction.

I have a L2TP/IPSec VPN configured on a Physical Mikrotik running v6. The solution is operational when connecting to this VPN from an Android tablet or an iOS mobile device, however I’m unable to connect using any Windows device. I have tested this on Windows 10/11 Professional and both systems exhibit the same issue.

The error I receive is: The L2TP connection attempt failed because the security layer encountered a processing error during initial negotiations with the remote computer.

Kind regards
Daniel

2

which version of windows??

for windows 10 works ok using default ipsec proposal, check that

/ip ipsec proposal
set [ find default=yes ] auth-algorithms=sha1 disabled=no enc-algorithms=aes-256-cbc,aes-192-cbc,aes-128-cbc lifetime=30m name=default pfs-group=modp1024
3

Thanks for the response.

I have checked and confirm I’m using the default proposal. The only difference is that the authentication algorithm includes both SHA1 and SHA256.

The issue is affecting both Windows 10 and Windows 11 Professional. It works as it should on Android & iOS devices.

Kind regards
Daniel

4

There are a range of issues that can cause the problem but one (that I really hope Microsoft fixed properly) was caused by an update Microsoft released in January 2022. Possibly this is causing your problem so see my post on this page for the patches to fix that update issue.

Possibly Microsft have released another update that causes the same problem (just guessing).