Hello,
I agree with Chetan."Thumbs up" to his advice.
In this case, you could us the "UnManaged Detector" as an option.
Upon booting, a computer sends out Address Resolution Protocol (ARP) traffic to identify itself on a network. Once enabled, the Unmanaged Detector listens for gratuitous ARP traffic and collects Internet Protocol (IP) and Machine Address (MAC) data from traffic passing it on the local network. This data is then forwarded to the Unmanaged Detector’s SEPM which compares the IP address and MAC address of detected systems against its known list of managed endpoint clients and reports on the unmanaged endpoint clients.
An unmanaged detector is configured by right-clicking a managed SEP client in the Clients page of the SEPM console, and selecting "Make unmanaged detector".
Best Practices: When to use the "Find Unmanaged Computers" or "Unmanaged Detector" features in Symantec Endpoint Protection 11.0
What does it mean to set a client as an Unmanaged Detector?
Hope that helps!!