FortiGate
FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
mle2802
Staff
Staff
Article Id 418246
Description This article describes how to troubleshoot the error 'certificate validation before EAP failed' when connecting to dial-up IPsec VPN after switching from signature to preshare key authentication.
Scope FortiGate.
Solution

When switching from signature authentication to the preshare key method combined with EAP in IKEv2, VPN clients may experience connection failure with the error 'certificate validation before eap failed'.

diagnose debug reset

diagnose debug application ike -1

diagnose debug enable


Screenshot 2025-11-08 130451.png


This issue can happen if the 'set eap-cert-auth enable' command was used before changing the authentication method from 'set authmethod signature” to “set authmethod psk'.

When switching to PSK using the command 'set authmethod psk', the 'set eap-cert-auth enable' option becomes hidden, but it still remains active in Phase1. To avoid problems, disable 'set eap-cert-auth' before changing the authentication method to PSK.

Screenshot 2025-11-08 161822.png
After disable 'set eap-cert-auth', try to reconnect VPN and confirm the connection.

Screenshot 2025-11-08 165356.png
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