Explorer II

Question

L2TP IPsec windows VPN error

Forum|Forum|3 years ago
October 19, 2022
4 replies
7723 views

Dear Team,

How to fixt this error -

The L2TP connection attempt failed because the security layer encountered a processing error during the initial negotiations.

FYI - I have configured L2TP IPsec vpn in Fortigate Firewall, I am getting error while connecting VPN.

How to resolve it and what are the troubleshooting stpes for it.

Thank you in advanced

FortiGate

jintrah_FTNT

Staff

Hi Umesh,

Please check the cookbook for some guidance Cookbook | FortiGate / FortiOS 6.2.0 | Fortinet Documentation Library

Best regards,

Jin

UmeshAuthor

Explorer II

Hi Jin,

I would like to tell you that I was able to access L2tp vpn from my windows machine and after 1 hour I was trying to connect again to access the network. then I am getting error.

even I have gone through Fortigate cook but issue could not be resolve till now.

Could you please tell me what can be possible issue .

thank you.

jintrah_FTNT

Staff

Hi,

The first post didnt mention that you connected l2tp successfully, and therefore cookbook reference for setting up the right configs were provided. Now that subsequent attempts are resulting in error, this could be from the windows machine or the path but configs on FortiGate is assumed fine since you connected earlier. On FortiGate, you can perform troubleshooting using the below commands when l2tp connections are attempted,

diagnose debug application ike -1

diagnose debug application l2tp -1

diagnose debug enable

Please see https://docs.fortinet.com/document/fortigate/6.0.0/Handbook/269357/troubleshooting-l2tp-and-ipsec

Best regards,

Jin

RachelGomez123

New Member

Tips to fix-

1. Check Your Regular Network Connection.
2. Make Sure the VPN Login Credentials Is Correct.
3. Try a Different VPN Server.
4. Reinstall VPN Software.
5. Disable IPv6 Protocol.
6. Troubleshoot VPN Not Connecting Windows 10 by Temporarily Disabling Firewall.

Regards,

Rachel Gomez

Regards,

Rachel Gomez

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