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mle2802
Staff
Staff
June 12, 2025

Troubleshooting Tip: Error 'unable to parse peer.subject as DN' with IPsec dial-up VPN using certificate authentication

  • June 12, 2025
  • 0 replies
  • 360 views
Description This article describes how to troubleshoot the error 'unable to parse peer.subject as DN' when using certificate authentication with IPsec dial-up VPN.
Scope FortiGate.
Solution Running ike debug while connecting to VPN, the error 'unable to parse peer.subject as DN' is observed:

diagnose debug application ike -1

diagnose debug enable

Screenshot 2025-06-11 122209.png

Comparing PKI user config under User & Authentication -> PKI with the client certificate, the 'Subject' field is different.

 

Screenshot 2025-06-11 120924.png

To resolve the error, change the PKI config to match the client certificate and test again:

Screenshot 2025-06-11 121847.png

 

Screenshot 2025-06-11 122038.png