Windows 10: L2TP VPN Failure after KB 5009543 contained in Security Update

I didn't see this posted in this Forum, so here it is if anybody is still looking, it affects W10 and 11https://support.microsoft.com/en-us/topic/january-17-2022-kb5010793-os-builds-19042-1469-19043-1469-and-19044-1469-out-of-band-f2d4f178-5b36-49cb-a6fd-4bf9857574f9

:)

 

Error: 788, when connecting to L2TP VPN

Hi there, recently I got this error when connecting to "L2TP/IPSec with certificate" VPN. I'm not sure what cause this.

I have already follow some of this steps with no luck :

• Adding AssumeUDPEncapsulationContextOnSendRule
• Restarting both IKE and IPSec services
• Allowing both CHAP and MS-CHAP v2
• Reset network connection
• Connect to different provider
• Re-adding VPN settings

There also little bit information can be found in the event viewer :

CoId={AEE0E2A8-34DF-41BB-B5F0-0458EFD41751}: The user xxx\xxx has started dialing a VPN connection using a per-user connection profile named yes. The connection settings are:

Dial-in User = *\

VpnStrategy = L2TP

DataEncryption = Requested

PrerequisiteEntry =

AutoLogon = No

UseRasCredentials = Yes

Authentication Type = PAP

Ipv4DefaultGateway = Yes

Ipv4AddressAssignment = By Server

Ipv4DNSServerAssignment = By Server

Ipv6DefaultGateway = Yes

Ipv6AddressAssignment = By Server

Ipv6DNSServerAssignment = By Server

IpDnsFlags =

IpNBTEnabled = Yes

UseFlags = Private Connection

ConnectOnWinlogon = No

IPsec authentication for L2TP = Machine certificate.

CoId={AEE0E2A8-34DF-41BB-B5F0-0458EFD41751}: The user xxx\xxx is trying to establish a link to the Remote Access Server for the connection named yes using the following device:

Server address/Phone Number = xxx.xxx.xxx.xxx

Device = WAN Miniport (L2TP)

Port = VPN3-1

MediaType = VPN.

CoId={AEE0E2A8-34DF-41BB-B5F0-0458EFD41751}: The user xxx\xxx dialed a connection named yes which has failed. The error code returned on failure is 788.

***Original title: VPN Error 788***

 

The second L2TP VPN can't connect.

I used ping , and there is no failure return.

The vpn server is built on ZyWall firewall, it is a L2TP over IPSec vpn,

I don't think it's the server's problem, because on PC2 using the same Wifi can connect to the vpn server perfectly.

 

Vpn ( trusted Vpn)

I use Nordvpn. You can connect 6 devices. You can choose servers by country or by a list of each server in each country, use UDP or HTTP, PPtP, L2TP. Double VPN, TOR via VPN. There`s are apps for android and iphones as well as DNS leak protection.