There are no prerequisites to take the Fortinet NSE 8 written exam. However, you must take the NSE 8 written exam before you can take the Fortinet NSE 8 practical exam. The written exam is not a certification by itself. You must pass both
the written exam and practical exam to obtain NSE 8 certification.
To prepare for the exams, we recommend that you take the NSE 4 to NSE 7 training courses and have comprehensive experience using Fortinet products in a production environment. The courses are optional.
Candidates who have passed the NSE 8 written exam might be interested in the NSE 8 Immersion workshop, which provides a better understanding of the level and complexity of the tasks and topology that are involved with the NSE 8 practical
For more information review the resources available at NSE 8 Library