Network Access Control (NAC) platforms authenticate and authorize every device attempting to connect to a corporate or campus network — wired, wireless, or VPN — enforcing policy based on device identity, posture, user role, and ongoing behavior. Core capabilities include 802.1X authentication, agentless device profiling and fingerprinting, posture assessment (patch level, security agent status, configuration compliance), dynamic VLAN assignment, quarantine and remediation workflows for non-compliant endpoints, and continuous monitoring of connected devices. NAC is the enforcement layer for network-level zero trust, maintaining a real-time inventory of everything on the network including corporate laptops, BYOD, IoT, and OT equipment. Leading vendors include Cisco ISE, HPE Aruba ClearPass, Forescout, Portnox, and Fortinet FortiNAC.