Windows 10 Error: 788, when connecting to L2TP VPN

[Syafi'i Azami]

Hi, recently I got this error when connecting to "L2TP/IPSec with certificate" VPN with Windows 10. I'm not sure what cause this since my friend can connect to it normally using same configuration and same routers.

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

• Adding AssumeUDPEncapsulationContextOnSendRule
• Restarting both IKA and IPSec services
• Allowing both CHAP and MS-CHAP v2
• Reset network connection
• Connect to different provider
• Re-adding VPN settings
• Allowing 500, 4500 in the inbound and outbound firewall rule
• Disable firewall

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.


I was wondering if some apps probably causing this error, but i have no idea which one.

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