Hi Raja,
Symantec NAC is a seprate Symantec product with seperate feature set. Basically Its comes with the Symantec Endpoint Protection, but you need to buy a seprate license for this feature to be enable. If you want to use this feature please keep in touch with symantec to purchase the same (
enterprise.support@symantec.com).
If this info helpful to you, please mark this as solution.
Thanks Samiron