Be it to learn the interface or preparing for NSE 5, 6, 7 exams, having the access to the real device is the best way to retain the information. Fortinet make available online access to all of their products for demo purposes, all for free. If not mentioned otherwise, the user/pass combo is demo/demo.
|Fortinet change, from time to time, passwords - in that case, you can request updated credentials for free at the page https://www.fortinet.com/demo-center/. You will get up-to-date password instantly to the email you specify. No phone/email verification is required.|
https://fortimail.fortidemo.com/admin/ FortiMail as Gateway
https://fortimail-srv.fortidemo.com/admin/Admin.html FortiMail as Server
https://fortiauthenticator.fortidemo.com/ FortiAuthenticator (user/pass: demo/demo1234$)
BTW, all devices are not really "demo", but actual physical/virtual appliances properly licensed and all. The only restriction is that demo user is read-only.
Example, Fortiweb demo: