5 Network Access Control (NAC) Best Practices

Network access control (NAC) is a security approach that identifies users and devices in order to authorize or deny varying levels of access to the network. Network administrators have long used NAC to keep networks secure and control network access.

Legacy NAC solutions built for on-premises environments cannot keep pace with cloud infrastructure or modern IT demands. These emerging technologies need advanced NAC solutions that can secure multiple endpoint devices and ensure only legitimate users gain access.

Getting NAC right takes more than picking a vendor. These five practices cover what needs to happen before, during, and after implementation to keep your network secure.

What Is a NAC Solution?

A NAC solution is a security solution that enforces security policy on every device that attempts to access a network, increasing network visibility and reducing the risk of unauthorized access and non-compliant devices reaching sensitive resources.

NAC verifies both the identity of those who are connecting and the state of the device itself, applying authentication, authorization, and ongoing monitoring to every endpoint.

Modern NAC solutions cover employees, contractors, guests, BYOD devices, and IoT endpoints — enforcing access policy from a single control plane. Many organizations implement NAC alongside 802.1X authentication to authenticate users and devices at the network layer before granting any access.

For a full breakdown of how NAC works, including architecture and authentication types, see our complete guide, What Is Network Access Control? NAC Explained.

Best Practices for Choosing the Right NAC Solution

Here are the best practices for selecting the right NAC framework for your organization.

1. Understand Your Organization’s NAC Solution Needs

Many organizations still rely on outdated authentication methods, such as password-based login, which exposes their devices to several vulnerabilities:

• Credential theft: Passwords can be phished, guessed, or reused across accounts.
• Credential sharing: Shared or written-down passwords remove any ability to trace access to a specific user.
• Misconfigured access controls: Copying another organization’s setup blindly leaves gaps that don’t fit your environment.

Warning: Don’t copy another organization’s NAC configuration wholesale. Access-control needs are specific to each environment, and inherited settings often leave gaps that don’t match your actual network.

Every organization has its own unique needs, so NAC implementation should be customized accordingly. Start with these three steps to determine the best fit for your organization:

1. Audit your current setup: Many organizations still rely on password-based authentication, which exposes devices to unnecessary risk.
2. Avoid copying other organizations’ configurations: Every network is different, so a policy that works well elsewhere may leave gaps in yours.
3. Check compatibility early: Many organizations run NAC alongside a virtual private network (VPN), so research fit and integration before committing to a solution.

2. Identify Areas That Require Access Control

When choosing a NAC solution, it’s important to understand where access control is most critical. The following areas typically require the most attention:

• IoT devices: Cameras, sensors, and other connected hardware often lack strong built-in security and need their own access rules.
• BYOD: Personal devices used for work need policies that separate them from company-owned endpoints.
• External users: Vendors, contractors, and guests need access that’s limited in scope and easy to revoke.
• Incident response: Have a plan ready for isolating or restricting a device the moment it shows signs of compromise.

Each of these areas presents its own unique vulnerabilities and access requirements.

By mapping out these needs before implementation, organizations can choose a NAC solution that provides the right level of control across every corner of their network — rather than a one-size-fits-all approach that leaves gaps in coverage.

3. Train Support Team in Network Access Control

There are some complexities involved in implementing a NAC solution. IT generalists may not be equipped to manage a full NAC deployment. Even if an organization outsources the implementation, it still needs to monitor policy and enforcement continuously, and on-premises deployments add appliance maintenance on top of that.

Having a dedicated team for access control can help organizations reduce dependencies on external vendors. A trained IT team can identify security threats caused by unauthorized or third-party access and prevent any damage. They can also train external users about the organization’s access control policy for secure and efficient collaboration.

At minimum, the team responsible for NAC should be trained to:

• Interpret posture and authentication alerts: Recognize when a device is flagged for non-compliance, a failed authentication, or anomalous behavior, and know how to respond.
• Manage quarantine and VLAN policies: Move non-compliant devices into restricted segments and restore access once issues are resolved.
• Onboard and offboard users and devices: Issue and revoke access as employees, contractors, and guests join or leave, without disrupting other users.
• Educate external users on access policy: Brief contractors and third parties on the organization’s requirements so collaboration stays secure and efficient.

4. Adopt Role-Based Access Control (RBAC)

Role-based access control assigns each user or device a level of network access based on their job function rather than granting broad, uniform access to everyone. A user’s role sets the baseline for access, while other attributes can further restrict access when the NAC solution makes its access decision.

Larger organizations need more granular roles, since responsibilities and required access vary widely across teams. The principle is the same at any size: grant each role the minimum access it needs to do its job, and nothing more. Assigning network access without reference to job function creates unnecessary exposure — a compromised low-level account shouldn’t be able to reach systems it never needed in the first place.

5. Use Multi-Factor Authentication (MFA)

As remote and hybrid work have become standard, employees increasingly need access to sensitive data and network resources from BYOD and IoT devices. That expanded access gives attackers more entry points to target, and they typically go after password-based logins, since credentials can be stolen or reused.

Network access control solutions allow network administrators to use multi-factor authentication (MFA) to authenticate users instead of relying solely on traditional passwords or IP address-based authentication. MFA allows organizations to:

• Add a second layer of verification: Combine passwords with a one-time code, phone call, or hardware token.
• Move toward certificate-based authentication: Certificates can serve as the possession factor within an MFA scheme when combined with another factor, such as a device PIN or biometric.
• Reduce helpdesk load: Fewer password resets happen when users authenticate through a certificate instead of a password.

Info: Certificate-based authentication provides strong authentication due to its encrypted EAP tunnel among various authentication protocols. It also enables clients to validate the RADIUS server’s identity using its server certificate.

SecureW2 JoinNow Cloud RADIUS simplifies certificate-based authentication with powerful policy enforcement engines that integrate with platforms like Microsoft Entra ID and Intune, and support granular, identity-based access control across your organization.

How Does a NAC Solution Work?

A NAC solution sits between a connecting device and the network it wants to reach, evaluating each connection request before any access is granted. The enforcement flow follows a consistent sequence regardless of vendor:

1. Detection: The NAC solution discovers and profiles every device that requests a connection, whether it is a managed laptop, a personal phone, or an unmanaged IoT endpoint.
2. Authentication: The device or user proves identity, ideally with a digital certificate over an encrypted Extensible Authentication Protocol (EAP) tunnel rather than a password that can be stolen or shared.

1. Posture assessment: The NAC solution checks the device’s health and compliance — operating system (OS) patch level, security software, and certificate validity — against organizational policy.
2. Authorization: Compliant devices are admitted with the access level their role allows. Non-compliant or unrecognized devices are denied, granted limited access, or quarantined in a restricted virtual local area network (VLAN).
3. Ongoing monitoring: The NAC solution continues to watch the session, revoking or restricting access in real time if a device falls out of compliance after it connects.

Types of NAC Solutions

Network access control solutions fall into two primary categories based on when enforcement is applied: pre-admission and post-admission.

Pre-Admission NAC

Pre-admission NAC evaluates a device before it is granted access to the network. When a device attempts to connect, the NAC solution checks its identity, health posture, and compliance against organizational policy.

Devices that fail the check due to missing patches, unmanaged endpoints, or unknown certificates are denied access or quarantined in a restricted VLAN. Pre-admission NAC is the primary enforcement model for organizations that need to prevent unauthorized devices from ever reaching internal resources.

Post-Admission NAC

Post-admission NAC monitors and enforces policy after a device has already connected to the network. Rather than blocking access at the perimeter, post-admission NAC watches for behavioral changes, policy violations, or posture drift during an active session.

If a device becomes non-compliant — for example, because a user installs unauthorized software — the NAC solution can revoke or restrict access in real time. Post-admission NAC is particularly valuable for environments with a high volume of guest devices or IoT endpoints where behavior changes frequently after initial connection.

Benefits of a NAC Solution

A NAC solution delivers value beyond simply blocking unknown devices. The main advantages organizations see are:

• Greater network visibility: A NAC solution discovers and profiles every device on the network, including unmanaged and previously unknown endpoints. This visibility is the foundation for every access decision that follows.
• Reduced attack surface: By admitting only authenticated, compliant devices, a NAC solution keeps unpatched and unmanaged endpoints from ever reaching sensitive resources. Pairing enforcement with VLAN segmentation contains any device that does slip through.
• Centralized policy enforcement: Rather than managing controls device by device, a NAC solution enforces endpoint and access policy from one central control plane, making it far easier to update rules as compliance requirements and threats evolve.
• Streamlined compliance reporting: Because a NAC solution logs who and what connects, when, and under which policy, it produces the access records auditors expect for frameworks such as HIPAA, PCI DSS, and SOX.

NAC and IoT Device Security

Internet of Things (IoT) devices present a distinct challenge for NAC because most lack a native authentication agent. Unlike a managed laptop, an IoT device cannot run software to verify identity and prove compliance. Still, organizations rely on a growing range of IoT devices, from biometric readers and IP cameras to medical hardware, making visibility and control essential.

NAC addresses this through two key mechanisms:

1. Certificate-based device identity embeds credentials directly into the device at provisioning, allowing each IoT device to be authenticated individually without requiring an agent.
2. VLAN segmentation then isolates IoT traffic from sensitive internal resources, containing any potential breach before it spreads.

Together, these capabilities allow organizations to apply granular access policies across every IoT device in their environment — closing a gap that traditional security tools often leave open.

Strengthen NAC With Certificate-Based Authentication

Certificate management is what separates a NAC deployment that can retire passwords from one that cannot. Digital certificates give organizations a stronger authentication layer than passwords alone, closing off one of the most common entry points for attackers.

The SecureW2 managed PKI solution, JoinNow Dynamic PKI, automates certificate enrollment across device types. It automates certificate enrollment through native integration with leading mobile device management (MDM) platforms, including Jamf and Intune, for zero-touch certificate delivery to managed devices.

Schedule your free demo to see how SecureW2 can help you deploy and manage a NAC solution built on certificate-based authentication.-ons.