I would like to contribute something today, we have VPN problems with our customers who use L2TP/IPsec (among others, this affects VPNs with Meraki MX and SonicWall): Mathias writes:įirst of all many thanks for your blog, it is an irreplaceable source for Windows problem solutions! I got then to the noon of 12 January 2022 still by mail a similar information. I uninstalled KB5009543 and now my L2TP VPNs work again.įrom German blog reader Mathias S.

There's two other confirmed reports in the Windows 10 subreddit. 'The L2TP connection attempt failed because the security layer encountered a processing error during initial negotiations with the remote computer'. Now their L2TP VPNs to different sites (All SonicWalls) are not working. Just rebooted two Win10 laptops that installed KB5009543 & KB5008876. The affected users writes:Īs the title says. But I got also feedback, that IKEv2 also didn't work with this update.Īt reddit there ist a thread KB5009543 – JanuBreaks L2TP VPN Connections, also confirming the issue. Update KB5009543 for Windows 10 20H2 – 21H2Īalso update KB5009543 for Windows 10 20H2 – 21H2 prevents VPN connection establishment with L2TP over IPSEC, as blog reader innocent bystander confirms in this German comment.īlog reader Joe mentions here that VPN tunnels using IKEv2 are not affected by this problem. Blog reader Julius has also posted links to external sources confirming the issue (see also below). Julius writes that after uninstalling the January security update, VPN connection establishment works fine again. For me, the problem occurs on all devices that received KB5009566 and also under different architectures (amd64 and arm64). In particular, VPN connections to Cisco Meraki MX appliances are affected.

The connection fails with the error message KB5009566 (Windows 11 22000.434) seems to cause some VPN connections (L2TP/pre-shared key/PAP) to stop working with the VPN client built into Windows 11. Got the first comment on the topic from German blog reader Julius, who describes the problem in connection with cumulative update KB5009566 for Windows 11 as follows (I've translated the German text): After Microsoft released the security updates for Windows as of January 11, 2022, I noticed various posts and comments as of Janureporting issues with VPN connections using L2TP over IPSEC.

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