Troubleshooting Tip: Possible reasons for FortiClient SSL VPN connectivity failure at specific percentages

sjoshi · ‎05-13-2022

Description

This article describes common causes of errors where the SSL VPN stops negotiating at specific percentages and offers solutions.

Scope

FortiOS.

Solution

The cause may vary depending on the percentage the negotiation stops at:

The error may be 'Unable to establish the VPN connection. The VPN server may be unreachable'.
The issue is usually due to a network connection.
Check whether the PC is able to access the internet and reach the VPN server on the necessary port.
Check whether the correct remote Gateway and port are configured in FortiClient settings.
Confirm whether the server certificate has been selected in FortiGate SSL VPN settings.
Check firewall policy to make sure there is at least one policy with Incoming Interface as SSL VPN tunnel interface (ssl.root).
Check restrictions based on Geolocation in SSL VPN settings or a local-in-policy that could prevent the endpoint from connection.
Try to reach VPN URL from the browser to confirm connectivity.
Check the router/modem's port-forwarding settings if there is another routing/internet-faced device before the firewall.

Negotiation stops at this percentage with error -5029. If this message appears, there is a mismatch in the TLS version. Check if the TLS version that is in use by the FortiGate is enabled on the client. Technical Note: How to limit the SSL and TLS versions of connections initiated by Forticlient explains how to check the TLS version.

This may occur when FortiClient generates a new pop-up window verifying whether the user wishes to proceed with a non-trusted TLS/SSL certificate.
It may mean a TLS version mismatch, which will also show as error -5029. If this message appears, there is a mismatch in the TLS version. Check if the TLS version that’s in use by the FortiGate is enabled on the client. Technical Note: How to limit the SSL and TLS versions of connections initiated by Forticlient explains how to check the TLS version.
An application or the FortiGate may cause this error. Check the local machine and network setup.
If the VPN server is unreachable with a (-5) error, see The VPN server may be unreachable. (-5)' errors.

4. 45%.

Negotiation stops at this percentage if there is any issue with authentication.
For local users, the issue could be just username/password being incorrect.
For the remote users, the issue is still related to authentication, but root causes can be different. Few possible reasons, FortiGate is unable to reach remote server, remote server sending authentication failure, secure connection failing for LDAPS.
Example: If negotiation stops at this percentage with the error 'ldap connection timeout', adjust the timeout settings:

config system global

set ldapconntimeout 300000
end

Refer to this article:

5. 48%.

Negotiation stops at this percentage if there is an issue with two-factor authentication.
If negotiation stops at this percentage with the error 'Credential or SSL VPN configuration is wrong (-7200)', recheck the credentials.
To resolve the 'Credential or SSL VPN configuration is wrong (-7200)' error, follow the steps in this article: Troubleshooting Tip: When logging in with SSL VPN, the error 'Credential or SSLVPN configuration is ....
Failure to connect via SSL VPN with 'Credential or SSL VPN configuration is wrong. (-7200)' message with 'sslvpn_login_cert_checked_error': Troubleshooting Tip: Failure to connect via SSL VPN with 'Credential or SSLVPN configuration is wron....
'Permission denied. (-455)' error. Check if the user is included in the user group that is configured in SSL VPN Authentication/Portal Mapping settings.
Host check requirement error (-455). If there is no host check enabled on VPN portals and users are still getting this error, check if the firewall has 'sslvpnd' daemon crashes. To check crash logs on FortiGate , execute this command:

diagnose debug crashlog read

6. 80%.

It may feature an error such as 'Unable to log on to the server. The username or password may not be configured properly for this connection'.
Negotiation stops at this stage due to issues with user privileges.
If negotiation stops at this stage, check whether the username and password were entered correctly.
Check the user and user group. This issue often occurs if the user is not in the correct user group with VPN access.
The -14 error of around 80% could be because of a user/group mismatch between the SSL VPN authentication rules and the Firewall policy for SSL VPN.
It is possible to have user and group configured but it must be exactly the same in SSL VPN authentication rules and Firewall policy.
If a user has a configured user group in the SSL VPN settings, always configure the user group in the firewall policy (follow this article: Technical Tip: FortiClient drops at 70-80% with no error message).
Verify the user is also matching the correct portal.
This issue may occur if a corresponding policy for the users has not been configured.
Additionally, check whether the correct Realm is being used and if any are configured.
If a user tries to log in from the local/guest user make sure the 'Restrict to Specific OS Versions' is disabled.
Look for host check/ MAC address check/ AV check is enabled.

7. 98%.

Issues at this stage indicate an inability to establish a tunnel after authentication is already completed.
Can be caused by network issues - for example, IPv6 to IPv4 connections (not supported), high network latency, blocked traffic, or traffic inspection between FortiClient and FortiGate.
This may be related to a corrupted FortiClient installation.