Vakhtang,
If you have purchased the NAC-ASSESS-LIC
You can use the built in application Saint, and or externally configure use of Nessus - if you have purchased that application.
Both are agentless assessment tools that will scan devices. They are not productive if the client has Windows Firewall or other similar applications installed. That is why agent based installed on a pc is a more secure solution. However in some public portal environments, that is not practical either.
To read more about implementation of Nessus or Saint, the help pages in Netsight are your best bet.
Here are some sample searches for Saint and Nessus