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Understanding the Issue: SSL VPN Connection Halt at 40%

The article outlines a fix for a problem in which SSL VPN connection attempts stop at 40% progress and show the error message 'VPN connection cannot be established. The VPN server might be unreachable. (-5).'

When encountering the issue where an SSL VPN connection attempt halts at 40% progress and displays the warning message ‘VPN connection cannot be established. The VPN server might be unreachable. (-5)’, it indicates that there is a problem with establishing a successful connection to the FortiGate SSL VPN server. This can stem from various factors, including network configuration issues, firewall settings, or client-side problems.

Step-by-Step Troubleshooting Guide

  1. Check Network Connectivity

    • Ensure that your device has internet access and can reach the FortiGate device’s public IP address.
    • Use tools like ping or traceroute to verify connectivity to the VPN server.

  2. Verify SSL VPN Configuration on FortiGate

    • Log into the FortiGate management interface.
    • Navigate to VPN > SSL-VPN Settings and confirm that:
      • The correct interface is selected for SSL VPN traffic.
      • The IP address range for clients is properly configured.
      • The authentication method (e.g., local users, LDAP) is correctly set up.

  3. Inspect Firewall Policies

    • Go to Policy & Objects > IPv4 Policy and ensure there are policies allowing traffic from the SSL VPN interface to internal resources.
    • Check if there are any restrictive policies that might block incoming connections.

  4. Review User Authentication Settings

    • Ensure that user accounts attempting to connect have valid credentials and are not locked out.
    • If using two-factor authentication, verify that it is functioning correctly.

  5. Examine Logs for Errors

    • Access logs through Log & Report > Event Log > VPN Events in the FortiGate interface.
    • Look for any error messages or warnings related to SSL VPN connections which could provide insight into what might be failing.

  6. Check Client-Side Configuration

    • Ensure that the FortiClient software is up-to-date on the client machine.
    • Verify that no local firewall or antivirus software is blocking the connection attempt.
    • Clear any cached configurations in FortiClient and re-enter your connection details.

  7. Test Different Connection Methods

    • If possible, try connecting from a different network (e.g., mobile hotspot) to rule out ISP-related issues.
    • Attempt using another device to see if the issue persists across multiple platforms.

  8. Update Firmware on FortiGate Device

    • Sometimes bugs in older firmware versions can cause connectivity issues; check if there’s an update available for your FortiGate unit and apply it if necessary.

  9. Consult Documentation and Support Resources

    • Refer to official Fortinet documentation regarding SSL VPN setup and troubleshooting for further guidance.
    • If all else fails, consider reaching out to Fortinet support for assistance with persistent issues.

By following these steps systematically, you should be able to identify and resolve the underlying cause of why your SSL VPN connection attempts halt at 40%.

Authoritative Sources Used in Answering this Question:

  • Fortinet Documentation: Official guides detailing configuration and troubleshooting processes for FortiGate devices.
  • Fortinet Knowledge Base: A repository of common issues and solutions provided by Fortinet support teams based on user experiences.
  • Network World Articles on VPN Technologies: Articles providing insights into common networking issues related to virtual private networks, including troubleshooting tips specific to various vendors like Fortinet.