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What is AAA (Authentication, Authorization, and Accounting)?

Author : PyNet Labs
Last Modified: March 18, 2024 
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In the vast realm of networking, AAA is an acronym that frequently appears, yet its meaning and significance often remain elusive to many. If you find yourself grappling with questions like “What is AAA in networking?” or “How does it impact network security?”, then you’ve come to the right place. In this blog, we will dive into the world of AAA and shed light on its crucial role in modern networking.

AAA stands for Authentication, Authorization, and Accounting. It is a set of services that provides more security for accessing network resources. AAA is a requirement, when it comes to network security.

So, without any further ado, let’s start with What is AAA.

What is AAA in Networking?

Authentication, Authorization, and Accounting (AAA) refers to a framework for intelligently controlling access to computer resources, enforcing policies, auditing usage, and providing the information required to bill for services. It forms the foundation upon which businesses, organizations, and service providers establish reliable mechanisms to authenticate users, enforce access privileges, and track resource utilization.

It forms the foundation upon which businesses, organizations, and service providers establish reliable mechanisms to authenticate users, enforce access privileges, and track resource utilization. So, here in AAA, we know that every single “A” has its own meaning. Let’s take a deep dive into the concept.


Authentication or we can say the verification of the user by having a valid username and password before getting access to any particular service or device.

A user must reveal personal information for Authentication. Users enter login information to verify their identity. When used as an identity and access management (IAM) tool, a AAA server verifies that a user’s login, password, and other authentication methods match those in its database of stored credentials.

The three methods of authentication are your fingerprint or other biometric, a USB key, and a password.


Once the user is authenticated, that user may be authorized for different types of access or activity. Authorization is a process via which we enforce policies for specific users according to the need.

A user can get access rights to particular parts of a network or system during authorization. A database also contains the user’s identification and the locations and sets of rights that have been granted to them. The privileges of the user can be modified by the administrator.  Authorization just verifies a user’s identity while authentication establishes the user’s privileges hence Authorization differs from authentication.

For example, an IT employee might not have the authority to modify the virtual private network (VPN) access passwords for the entire firm.  However, the network administrator has the option to provide the member access rights, allowing them to change each user’s VPN password. The team member will then be given permission to enter a location they had previously been denied access to.

Like here we have –

  • Privileges and restrictions (for specific users)


Accounting is defined as keeping track of things done inside the network as the name represents that to keep a log of tracks which can include the total amount of consumed time and data. This information of logs and tracks can be used for audit and reporting.

Accounting can be used to audit user activity, identify user trends, and produce more precise billing. Utilizing the information gathered during the user’s access will enable this. For instance, the time logs produced by the accounting system can record how long a user was logged in to the router and inside the system, and then charge them appropriately, if the system bills users by the hour.

For example, with accounting, you could get logs and every update when the user logged in and when the user logged out.

Now that we have a good understanding of AAA in networking, let’s understand its importance.

Why is AAA important in Network Security?

The answer to this question is simple because AAA is something that is a crucial piece of every infrastructure.

AAA is something through which we can ensure our network is secure by allowing access to specific users with specific policies and complete logs of what user does when they log in upto log out.

AAA Configuration

But before AAA, we also have some terminal lines and password protection,

  1. Console Port – This port is mainly used for local system access, and access can be taken physically via the console terminal.
  2. VTY Lines (Virtual Terminal) – It is used for telnet and SSH configurations.

Now that you have learned what is AAA, let’s move on and understand how it is implemented.

Implementation of AAA in Networking

There are mainly two ways for implementing AAA in networking –

1. ACS Server

This strategy is widely used. The router and the ACS must both be configured for AAA. The external ACS server, which could be an ACS device or software running on VMware, is used. The configuration includes the creation of a user and a special customized method list for authentication, authorization, and accounting.

After receiving requests for authentication from the client or Network Access Server (NAS), the ACS server determines whether to provide the user access to the network resource or not based on the credentials provided by the user.

2. Local Database

If we want to implement AAA using the local operating configuration of the router or switch, we must first create users for authentication and grant them privilege levels for authorization.

Components of AAA in Networking

  • Supplicant (End devices which are used for device access like PC, Laptop)
  • Authenticator (Switches, WLAN Controllers these devices don’t authenticate, but they simply forward the credential to another device called an authentication server)
  • Authenticate Server (validates the identity of client) – The device that takes user or client credentials and permits or denies network access based on a user database and policies.

These are the three AAA components. Now, it’s time to take a look at AAA protocols.

AAA Protocols

There are several types of AAA Protocols –


TACACS+ stands for Terminal Access Controller Access-Control System Plus. It uses the client/server model to connect users. TACACS+ functions by supplying a secret key known only to the client and the TACACS+ system. The connection is allowed to proceed when a valid key is given.


RADIUS stands for Remote Authentication Dial-In User Service. RADIUS is a networking protocol that uses a client/server architecture to carry out AAA operations for users on a distant network. Users attempting to access the network are concurrently granted authorization and authentication using RADIUS. All AAA data packets are also taken by RADIUS and encrypted to add an additional layer of protection.


The Diameter protocol is a AAA protocol that works with LTE and multimedia networks. Diameter is a development of RADIUS, and is specifically developed to optimise LTE connections and other types of mobile networks.

Difference between TACACS + and RADIUS –

Cisco proprietary protocol.IETF Open Standard.
Uses TCP port number 49Uses UDP port 1812 for authentication
Majorly used for AAA device access and also used for network access.Uses UDP port 1813 for accounting.
Advance accounting service.It can be used for accessing the network devices.

Another major difference between TACACS+ and RADIUS is that RADIUS needs to return every authorization parameter in one single reply, whereas TACACS+ can request authorization parameters separately and multiple times throughout a session.

For example, a network device, such as a switch or a router, can request a TACACS+ server to individually authorize every command that a user tries to implement after logging in to the device.

Whereas, RADIUS requires those commands to be sent in the starting authentication response, and since there can be a lot of CLI command combinations, a large authorization result list could cause maximum utilization of resources on the network device. This is one of a reason TACACS+ is preferred for network device access.

Advantages of AAA Framework

There are many advantages related to AAA in networking. Some of them are –

  • The scalability of a network is improved by the AAA framework.
  • It makes the network more flexible and controllable.
  • It helps in standardizing protocol usage across the network.
  • Using RADIUS, each user receives a unique set of credentials.
  • Users will have a single point of contact, while IT administrators will employ system authentication.

Disadvantages of AAA Framework

The following is a list of some of the major drawbacks of the AAA in networking:

  • Configuring a RADIUS server can be difficult and time-consuming, especially the initial configuration.
  • The finest RADIUS server software and deployment approach for your business can be difficult to choose.
  • Hardware maintenance on-site can be challenging and time-consuming.

Frequently Asked Questions

Q1 – What is AAA server in networking?

An AAA server in networking refers to an Authentication, Authorization, and Accounting server. It is responsible for managing user access, determining their privileges, and tracking their usage within a networked system. The AAA server plays a critical role in enforcing security policies, controlling network access, and ensuring accountability for network activities.

Q2 – What are the AAA protocols?

The commonly used AAA protocols in networking are RADIUS (Remote Authentication Dial-In User Service) and TACACS+ (Terminal Access Controller Access-Control System Plus). RADIUS provides centralized authentication, authorization, and accounting services for remote network access, while TACACS+ offers similar functionality with additional support for authorization and command accounting in network device administration.

Q3 – How AAA authentication works?

AAA authentication works by following a three-step process:

  • Authentication: The user provides credentials such as a username and password.
  • Authorization: Once the user is authenticated, their access privileges and permissions are determined based on predefined policies.
  • Accounting: The system tracks and logs the user’s activities, including usage details and resource consumption, for auditing and billing purposes.

Q4 – What are the 3 A’s in cyber security?

The three A’s in cybersecurity refer to the principles of Authentication, Authorization, and Accounting. Authentication ensures the verification of user identities and establishes trust. Authorization determines the access privileges and permissions granted to authenticated users. Accounting tracks and monitors user activities for auditing, compliance, and billing purposes.


In conclusion, AAA in networking form the backbone of secure and efficient digital systems. Authentication validates user identities, ensuring only authorized individuals gain access. Authorization assigns appropriate privileges, safeguarding sensitive resources. Lastly, accounting tracks and records user activities, facilitating accountability and compliance. By implementing robust measures for authentication, authorization, and accounting, organizations can establish strong security foundations and protect their valuable assets in today’s interconnected world.

We hope you found everything you were looking for in the “What is AAA in Networking” article.

AAA is an integral part of PyNet Labs’ CCNA and CCNP Training. You can check out all our courses from the “All Courses” menu here or by clicking this link – PyNet Labs Courses. Our CCNP ENCOR training is among the highest-rated Cisco training course online, with an average rating of 4.9 out of 5.

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