Which technology is the leading industry approach used to automatically enforce NAC?

SNMP is used for network device monitoring and management via polling and traps, and has no built-in mechanism to enforce access control decisions.

Port security restricts access using statically configured MAC address lists per switch port and is not a scalable or automated NAC enforcement mechanism.

IGMP is a network-layer protocol that manages multicast group membership and plays no role in authenticating or controlling network access.

802.1X is an IEEE standard for port-based access control that works with RADIUS servers and Extensible Authentication Protocol (EAP) to automatically authenticate and authorize devices before granting network access. It enforces NAC policies dynamically - allowing, quarantining, or blocking devices - without manual intervention, making it the leading industry approach for automated NAC.