How to use network access control (NAC)

· Category: Cybersecurity

Short answer

NAC ensures that only compliant and authenticated devices can access the network. It enforces policies at the point of entry.

Steps

  1. Define policies: Specify required antivirus status, OS patch levels, and configuration baselines.

  2. Deploy 802.1X: Use port-based authentication so switches or wireless controllers block non-authenticated devices.

  3. Integrate with identity: Connect NAC to Active Directory or RADIUS for user and machine authentication.

  4. Assess endpoints: Run agents or agentless scans to check device health before granting access.

  5. Enforce remediation: Quarantine non-compliant devices in an isolated VLAN with limited access to patching servers.

  6. Monitor and audit: Review access logs and policy violations regularly.

Tips

  • Start with monitoring mode before enforcing quarantine to avoid business disruption.
  • Support guest access through a captive portal on a segmented VLAN.
  • Keep agent software updated to prevent bypass techniques.

Common issues

  • Misconfigured RADIUS shared secrets causing authentication failures.
  • Legacy devices without 802.1X support requiring MAC authentication bypass.
  • Certificate expiration on supplicants blocking valid devices.