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What is NAC

This document describes the definition and purpose of NAC, the comparison of the three authentication methods and the relationship between NAC and AAA.
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What is NAC

What is NAC

What is NAC


Network Admission Control (NAC) is an end-to-end access security framework and includes 802.1X authentication, MAC address authentication, and Portal authentication.

With the development of enterprise network, threats increasingly bring risks, such as viruses, Trojan horses, spyware, and malicious network attacks. On a traditional enterprise network, the intranet is considered as secure and threats come from extranet. However, 80% security threats actually come from the intranet. The intranet threats will cause serious damage in a wide range. Even worse, the system and network will break down. In addition, when intranet users browse websites on the external network, the spyware and Trojan horse software may be automatically installed on users' computers, which cannot be sense by the users. The malicious software may spread on the internal network.

The traditional security measures cannot meet requirements on border defense due to increasing security challenges. The security model should be converted into active mode to solve security problems from the roots (terminals), improving information security level of the entire enterprise.

The NAC solution integrates terminal security and access control and takes the check, audit, secure, and isolation measures to improve the proactive protection capability of terminals. This solution ensures security of each terminal and the entire enterprise network.

As shown in the following diagram, NAC includes three components: NAC terminal, network access device, and access server.

  1. Typical NAC networking diagram

  • NAC terminal: functions as the NAC client and interacts with network access devices to authenticate access users. If 802.1X authentication is used, users must install client software.
  • Network access device: function as the network access control point that enforces enterprise security policies. It allows, rejects, isolates, or restricts users based on the security policies customized for enterprise networks.
  • Access server: includes the access control server, management server, antivirus server, and patch server. It authenticates users, checks terminal security, repairs and upgrades the system, and monitors and audits user actions.


Traditional network security technologies focus on threats from external computers, but typically neglect threats from internal computers. In addition, current network devices cannot prevent attacks initiated by devices on internal networks.

The NAC security framework was developed to ensure the security of network communication services. The NAC security framework improves internal network security by focusing on user terminals, and implement security control over access users to provide end-to-end security.

Comparison Between Three NAC Authentication Modes

NAC provides 802.1X authentication, MAC address authentication, and Portal authentication. You can select a proper authentication mode or a combination of multiple authentication modes based on your application scenarios. The combination of multiple authentication modes varies according to the device type and configuration. Table 1 compares the three NAC authentication modes.

Table 1-1 Comparison between NAC authentication modes


802.1X Authentication

MAC Address Authentication

Portal Authentication

Application scenario

New network with concentrated users and high requirements for information security

Authentication of dumb terminals such as printers and fax machines

Scenario where users are sparsely distributed and move frequently



Not required

Not required


High security

No client required

Flexible deployment


Inflexible deployment

Complex management and MAC address registration required

Low security


To configure NAC, you must enable authentication, authorization, and accounting (AAA). NAC and AAA work together to implement access authentication.

  • NAC is used for interaction between users and access devices. It controls the user access mode (802.1X, MAC address, or Portal), as well as the parameters and timers used during network access. NAC ensures secure and stable connections between authorized users and access devices.
  • AAA is used for interaction between access devices and authentication servers. AAA provides authentication, authorization, and accounting for access users to control their network access rights.
Updated: 2019-06-04

Document ID: EDOC1100086561

Views: 918

Downloads: 80

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