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.
This article describes the case when logging into the FortiClient it shows the following error 'Unable to establish VPN connection. The VPN server may be unreachable(-6005)'.
Scope
FortiClient, FortiGate.
Solution
When trying to establish a VPN connection, users receive an error message that says 'Unable to establish VPN connection. The VPN server may be unreachable (-6005)'.
Check the configuration if everything is correct. This error is usually caused by an incorrect VPN gateway configuration, or incorrect authentication configuration in the case of SAML authentication.
Ensure it is possible to connect and pass authentication using the configured VPN gateway URL from the browser. This does not require enabling web access: it should be possible to see a login page even with tunnel only access enabled.
The issue can sometimes be resolved by uninstalling the current version of FortiClient.
Consider using wired internet connections (Ethernet) over wireless if persistent connectivity issues are faced.
Remember that VPN connections might not work on certain networks (e.g., some public Wi-Fi networks block VPN connections), so always test on a known good network if in doubt.
Reinstall the same version of FortiClient or consider upgrading to a newer version if available.
Newer versions may contain bug fixes.
If the issue is recurrent, consider generating and reviewing FortiClient logs to pinpoint any underlying issues. Share these with the IT department or Fortinet support for a deeper diagnosis.
