USG 20W create VPN connection from Windows 10

Vicente Posts: 1
edited April 2021 in Security
I am trying to configure an L2TP connection with the USG20W as a server and a remote Windows 10 client using the Windows client with L2TP under IPsec
I have not been able to connect, the error that Windows returns is "The L2TP connection attempt failed because the security level could not negotiate compatible parameters with the remote computer"
In the Event Viewer the error is 788
I have followed the instructions in this message but I have not been able to solve it either:

Zyxel firmware is 3.30 (BDR.9)

The truth is that a practical case of complete configuration of a VPN with this device would be useful, since it has many options and I am only finding partial things or very simple manuals that later do not work because many parameters are missing that I am not able to locate later. It is very complicated for me.


All Replies

  • Zyxel_Can
    Zyxel_Can Posts: 342  Zyxel Employee
    Friend Collector First Answer First Comment

    Hi @Vicente,


    Can you please share some information with us;


    1 – Can you please check Monitor > Log when you try to connect with L2TP connection and paste the Log into this post?


    2- Can you please make sure about following information;

    a.    Configuration > VPN Gateway > $GatewayName$ > Negotiation Mode : Main

    b.    Configuration > VPN Connection > $ConnectionName$ > Policy > Local Policy : IP Address of the Gateway

    c.    Configuration > VPN Connection > $ConnectionName$ > Phase 2 Settings > Advance > Encapsulation : Transport

    3- If that doesn’t solve the problem, you can post the screenshot of your USG20W configuration or you can provide your configuration file to me by private message for further check.



    Best regards.

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