The correct answer is 802.1X, which is an identity-based Network Access Control (NAC) framework emphasized in the CompTIA Network+ N10-009 objectives under network security and access control. 802.1X uses a policy-driven authentication process to determine whether a user or device is allowed network access based on verified credentials, such as usernames, passwords, or digital certificates.

802.1X operates using three main components: the supplicant (the client requesting access), the authenticator (the network device such as a switch or wireless access point), and the authentication server (typically a RADIUS server). Once the user’s identity is authenticated, predefined policies determine the level of access granted—full access, limited access, or denial. This makes 802.1X a cornerstone of zero trust and enterprise-grade NAC implementations.

A standard ACL controls traffic based on IP addresses and ports, not user identity. MAC filtering allows or denies access based on device MAC addresses, which can be easily spoofed and does not verify user identity. SSO (Single Sign-On) simplifies authentication across multiple systems but does not control network-layer access.

Network+ highlights 802.1X as a secure, scalable solution for enforcing identity-based network access policies in both wired and wireless environments.