Troubleshooting FSSO

Troubleshooting FSSO

When installing, configuring, and working with FSSO some problems are quite common. A selection of these problems follows including explanations and solutions.

Some common Windows AD problems include:

  • General troubleshooting tips for FSSO
  • Users on a particular computer (IP address) can not access the network
  • Guest users do not have access to network


General troubleshooting tips for FSSO

The following tips are useful in many FSSO troubleshooting situations.

  • Ensure all firewalls are allowing the FSSO required ports through.

FSSO has a number of required ports that must be allowed through all firewalls or connections will fail. These include: ports 139, 389 (LDAP), 445, 636 (LDAP).

  • Ensure there is at least 64kbps bandwidth between the FortiGate unit and domain controllers. If there is insufficient bandwidth, some FSSO information might not reach the FortiGate unit. The best solution is to configure traffic shaping between the FortiGate unit and the domain controllers to ensure that the minimum bandwidth is always available.


Users on a particular computer (IP address) can not access the network

Windows AD Domain Controller agent gets the username and workstation where the logon attempt is coming from. If there are two computers with the same IP address and the same user trying to logon, it is possible for the authentication system to become confused and believe that the user on computer_1 is actually trying to access computer_2.

Windows AD does not track when a user logs out. It is possible that a user logs out on one computer, and immediate logs onto a second computer while the system still believes the user is logged on the original computer. While this is allowed, information that is intended for the session on one computer may mistakenly end up going to the other computer instead. The result would look similar to a hijacked session.



  • Ensure each computer has separate IP addresses.
  • Encourage users to logout on one machine before logging onto another machine.
  • If multiple users have the same username, change the usernames to be unique.
  • Shorten timeout timer to flush inactive sessions after a shorter time.


Guest users do not have access to network

A group of guest users was created, but they don’t have access.



The group of the guest users was not included in a policy, so they do not fall under the guest account. To give them access, associate their group with a security policy.

Additionally, there is a default group called SSO_Guest_Users. Ensure that group is part of an identity-based security policy to allow traffic.


Having trouble configuring your Fortinet hardware or have some questions you need answered? Check Out The Fortinet Guru Youtube Channel! Want someone else to deal with it for you? Get some consulting from Fortinet GURU!

Don't Forget To visit the YouTube Channel for the latest Fortinet Training Videos and Question / Answer sessions!
- FortinetGuru YouTube Channel
- FortiSwitch Training Videos

Cybersecurity Videos and Training Available Via: Office of The CISO Security Training Videos