SSL VPN troubleshooting

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This page contains tips to help you with some common challenges for SSL VPN.

  • Enter the following to display debug messages for SSL VPN:
diagnose debug application sslvpn -1

This command enables debugging of SSL VPN with a debug level of -1. The -1 debug level produces detailed results.

  • Enter the following command to verify the debug configuration:
diagnose debug info
debug output: disable
console timestamp: disable
console no user log message: disable
sslvpn debug level: -1 (0xffffffff)
CLI debug level: 3

This output verifies that SSL VPN debugging is enabled with a debug level of -1, and shows what filters are in place. The output above indicates that debug output is disabled, so debug messages are not displayed. The output also indicates that debugging has not been enabled for any software systems.

  • Enter the following to enable displaying debug messages:
diagnose debug enable

To view the debug messages, log into the SSL VPN portal. The CLI displays debug output similar to the following:

FGT60C3G10002814 # [282:root]SSL state:before/accept initialization (172.20.120.12)
[282:root]SSL state:SSLv3 read client hello A (172.20.120.12)
[282:root]SSL state:SSLv3 write server hello A (172.20.120.12)
[282:root]SSL state:SSLv3 write change cipher spec A (172.20.120.12)
[282:root]SSL state:SSLv3 write finished B (172.20.120.12)
[282:root]SSL state:SSLv3 flush data (172.20.120.12)
[282:root]SSL state:SSLv3 read finished A:system lib(172.20.120.12)
[282:root]SSL state:SSLv3 read finished A (172.20.120.12)
[282:root]SSL state:SSL negotiation finished successfully (172.20.120.12)
[282:root]SSL established: DHE-RSA-AES256-SHA SSLv3 Kx=DH Au=RSA Enc=AES(256) Mac=SHA1
  • Enter the following to stop displaying debug messages:
diagnose debug disable

 

The following is a list of potential issues. The suggestions below are not exhaustive, and may not reflect your network topology.

There is no response from the SSL VPN URL.

  • Go to VPN > SSL-VPN Settings and check the SSL VPN port assignment. Also, verify that the SSL VPN policy is configured correctly.
  • Check the URL you are attempting to connect to. It should follow this pattern:
https://<FortiGate IP>:<Port>/remote/login
  • Ensure that you are using the correct port number in the URL.

FortiClient cannot connect.

Read the Release Notes to ensure that the version of FortiClient you are using is compatible with your version of FortiOS.

Tunnel-mode connection shuts down after a few seconds.

This issue can occur when there are multiple interfaces connected to the Internet (for example, a dual WAN). Upgrade to the latest firmware then use the following CLI command:

config vpn ssl settings
   set route-source-interface enable
end

When you attempt to connect using FortiClient or in Web mode, you are returned to the login page, or you receive the following error message: “Unable to logon to the server. Your user name or password may not be configured properly for this connection. (-12).

  • Ensure that cookies are enabled in your browser.
  • If you are using a remote authentication server, ensure that the FortiGate is able to communicate with it.
  • Access to the web portal or tunnel will fail if Internet Explorer has the privacy Internet Options set to High. If set to High, Internet Explorer will block cookies that do not have a compact privacy policy, and that use personally identifiable information without your explicit consent.

You receive an error message stating: “Destination address of Split Tunneling policy is invalid.

The SSL VPN security policy uses the ALL address as its destination. Change the address to that of the protected network instead.

The tunnel connects but there is no communication.

Go to Network > Static Routes and ensure that there is a static route to direct packets destined for the tunnel users to the SSL VPN interface.

You can connect remotely to the VPN tunnel but are unable to access the network resources.

Go to Policy & Objects > IPv4 Policy and examine the policy allowing VPN access to the local network. If the destination address is set to all, create a firewall address for the internal network. Change the destination address and attempt to connect remotely again.

Users are unable to download the SSL VPN plugin.

Go to VPN > SSL-VPN Portals to make sure that the option to Limit Users to One SSL-VPN Connection at a Time is disabled. This allows users to connect to the resources on the portal page while also connecting to the VPN through FortiClient.

Users are being assigned to the wrong IP range.

Ensure that the same IP Pool is used in VPN Portal and VPN Settings to avoid conflicts. If there is a conflict, the portal settings will be used.

Sending tunnel statistics to FortiAnalyzer

By default, logged events include tunnel-up and tunnel-down status events. Other events, by default, will appear in the FortiAnalyzer report as “No Data Available”. More accurate results require logs with action=tunnel-stats, which is used in generating reports on the FortiAnalyzer (rather than the tunnel-up and tunnel-down event logs). The FortiGate does not, by default, send tunnel-stats information.

To allow VPN tunnel-stats to be sent to FortiAnalyzer, configure the FortiGate unit as follows using the CLI:

config system settings
   set vpn-stats-log ipsec ssl
   set vpn-stats-period 300
end

 

Fortinet Technical Documentation

Fortinet Technical Documentation

Contact Fortinet Technical Documentation at techdoc@fortinet.com.
Fortinet Technical Documentation

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