NAC

What NAC Controls

Network Access Control systems authenticate and authorize devices before permitting them to connect to a network segment. A NAC agent on the device reports identity (user credentials, device certificate) and posture (OS patch level, antivirus status, disk encryption state) to a NAC policy server. Based on this assessment, the NAC system places the device in an appropriate VLANVirtual Local Area Network. A logical network segmentation technique that groups devices into separate broadcast domains regardless of physical location, using IEEE 802.1Q tagging. VLANs improve security, performance, and manageability. — full access for compliant corporate devices, a restricted quarantine VLAN for unpatched machines, and a guest VLAN for unauthenticated visitors.

802.1X and Enforcement Points

The most common NAC protocol is IEEE 802.1X, which authenticates devices at the Ethernet port or Wi-Fi association stage before assigning an IP address. The supplicant (device) communicates with an authenticator (switch or access point) that proxies to a RADIUS server acting as the authentication backend. Before 802.1X, MAC address filtering provided weak NAC — easily bypassed by address spoofing. Post-admission NAC extends control beyond initial access by continuously checking device posture and revoking access when compliance drifts.

NAC in Zero-Trust Architectures

NAC is a foundational component of zero-trust Network SegmentationThe practice of dividing a network into smaller, isolated segments to limit the blast radius of security breaches and improve performance. Implemented through VLANs, subnets, firewalls, or micro-segmentation in zero-trust architectures.. It ensures that even devices on trusted VLANVirtual Local Area Network. A logical network segmentation technique that groups devices into separate broadcast domains regardless of physical location, using IEEE 802.1Q tagging. VLANs improve security, performance, and manageability.s are authenticated and compliant, not merely physically connected. Integration with Active Directory, certificate authorities, and mobile device management platforms enables automated policy enforcement. IoTInternet of Things. The network of physical devices (sensors, cameras, appliances, vehicles) embedded with connectivity and software that collect and exchange data over the internet. IoT devices often use protocols like MQTT and CoAP. devices — which cannot run 802.1X supplicants — are handled through MAC authentication bypass with aggressive FirewallA network security device or software that monitors and filters incoming and outgoing traffic based on predefined rules. Firewalls can block traffic by IP address, port number, protocol, or application-layer content. restrictions applied to their segment. Open Port Checker helps verify that NAC-controlled devices can reach only permitted services.