What is Network Access Control?

Last Updated : 27 May, 2025

Network Access Control (NAC) is a security solution that uses a set of protocols to prevent unauthorized users and devices from accessing a private network or to grant restricted access to devices that comply with network security policies. It is also known as Network Admission Control.

NAC is responsible for network management and security by enforcing security policies, ensuring compliance, and managing access control.
It operates across both wired and wireless networks by identifying and evaluating the devices that attempt to connect.
To set up a NAC solution, administrators define protocols that determine how devices and users are authenticated and authorized for different levels of access.
Access rules are typically based on factors such as the device being used, the location of access, the user's access rights, and the specific data or resources being requested.

Types of Network Access Control

Different types of network access control are:

Pre-admission

It happens before access to the network is granted on initialization of request by user or device to access the network. It evaluates the access attempt and only allows the access if the user or device is compliant with organization security policies and authorized to access the network.

Post-admission

It happens within the network when the user or device attempts to access the different parts of the network. It restricts the lateral movement of the device within the network by asking for re-authentication for each request to access a different part of the network.

Steps to Implement NAC Solutions

Following are the steps to implement NAC solutions:

Gather Data: Perform an exhaustive survey and collect information about every device, user, and server that has to interface with the network resources.
Manage Identities: Verify user identities within the organization by authentication and authorization.
Determine Permissions: Create permission policies stating different access levels for identified user groups.
Apply for Permissions: Apply permission policies on identified user groups and register each user in the NAC system to trace their access level and activity within the network.
Update: Monitor security operations and make adjustments to permission policies based on changing requirements of the organization with time.

Importance of Network Access Control

There has been exponential growth in the number of mobile devices accessing private organizational networks in recent years.
This surge has increased security risks to organizational resources.
To address these risks, tools are needed that offer visibility, access control, and compliance enforcement to strengthen network security.
Network Access Control (NAC) systems can:
- Deny access to non-compliant or unauthorized devices.
- Grant restricted access to devices that partially meet security policies.
- Prevent insecure devices from infecting or compromising the network.
NAC solutions are capable of managing large enterprise networks with a wide variety of device types.

Key Responsibilities of Network Access Control

It allows only compliant, authenticated devices to access network resources and infrastructure.
It controls and monitors the activity of connected devices on the network.
It restricts the availability of network resources of private organizations to devices that follow their security policy.
It regulates the access of network resources to the users.
It mitigates network threats by enforcing security policies that block, isolate, and repair non-compliant machines without administrator attention.

Real Life NAC Examples

Corporate Office : NAC ensures only company-issued, secure laptops can access internal systems. Unapproved or non-compliant devices are blocked or sent to a restricted network.
Hospital / Healthcare : NAC verifies that medical devices and staff computers meet security standards before accessing patient data. Non-compliant devices are denied or limited in access.
University Campus : Students must meet basic security requirements (like antivirus) to use campus Wi-Fi. NAC segments student and faculty traffic to protect academic resources.
Retail Store : It restricts access so only authorized point-of-sale systems connect to the network. Customer and staff devices are placed on a separate guest Wi-Fi.
Smart Home : It checks smart devices before letting them connect. Guests get internet access only, keeping home automation systems secure.

Principle Elements of NAC

There are mainly three principle elements of NAC which are:

Access Requestor(AR)

An Access Requestor (AR) is any entity such as a device, user, or process that attempts to gain access to network resources. This could include servers, IP cameras, printers, or other IP-enabled devices managed by the NAC system.

ARs are sometimes referred to as supplicants or clients. To ensure security, ARs must comply with the organization's specific policies or guidelines. This process ensures that unauthorized entities are denied access to protected resources.

Policy Server

The policy server determines what level of access should be granted to an Access Requestor (AR) based on:

The AR’s identity.
Its permission level.
The nature of the access request.
The organization's predefined access policies.

It often relies on backend services like:

Antivirus software
Patch management systems
User directories (e.g., Active Directory)

The policy server evaluates the state of the host and uses the organization's rules to either:

Authorize access if the AR complies with policies
Deny or restrict access if the AR does not comply

Network Access Server(NAS)

Users connecting to an organization's internal network from distant locations utilize the NAS as an access control point. These often serve as VPNs and give users access to the company's internal network. These days, NAS functionality is frequently included in policy server systems.

Remote employees can connect to the company's internal network via NAS, which serves as an access point for them. This allows the company and its employees to create a secure connection and grant authorized access to the network.

Benefits of Network Access Control (NAC)

Enhanced Authentication: Users can be required to authenticate using multi-factor authentication (MFA), offering much stronger security than traditional IP address or username/password methods.
Granular Network Protection: NAC enables segment-based access control, adding additional layers of security around specific areas or resources within the network.