RADIUS (Remote Authentication Dial-In User Service) and TACACS+ (Terminal Access Controller Access-Control System Plus) are both protocols used for network access control and AAA, particularly with Cisco devices. Here's a comparison between the two:


  1. Purpose: Both RADIUS and TACACS+ are used for centralized authentication, authorization, and accounting (AAA) of users accessing network resources.
  2. Usage in Networking: They are commonly implemented in enterprise networks for controlling access to routers, switches, and other network devices, particularly in Cisco environments.
  3. Encryption: Both protocols provide a measure of security by encrypting certain elements of the communication.


  1. Protocol Operation:
    • RADIUS: Combines authentication and authorization as a single function. It is a UDP-based protocol, which makes it less reliable but faster.
    • TACACS+: Separates authentication, authorization, and accounting as distinct services. It uses TCP, offering more reliable connections.
  2. Encryption:
    • RADIUS: Encrypts only the password in the access-request packet.
    • TACACS+: Encrypts the entire body of the packet, offering more security for the authentication and authorization information.
  3. Granular Control:
    • RADIUS: Provides less granular control of authorization for different commands.
    • TACACS+: Offers more detailed control over user commands, allowing administrators to restrict specific commands based on user profiles.
  4. Interoperability:
    • RADIUS: More widely supported and can be used with a variety of network equipment vendors.
    • TACACS+: Largely Cisco-centric and best suited for networks primarily using Cisco equipment.
  5. Accounting Features:
    • RADIUS: Offers more extensive accounting features, making it preferable for tracking user activity and billing purposes, although it does not provide command-level accounting.
    • TACACS+: While it does support accounting, it is less comprehensive compared to RADIUS, although it does provide command-level accounting.
  6. Multi-Factor Authentication:
    • RADIUS: Generally better support for third-party MFA solutions.
    • TACACS+: Support for MFA is possible but might be more complex to integrate with third-party solutions.

Use with Cisco Devices

  • TACACS+ is often preferred in Cisco environments due to its superior integration with Cisco devices, offering more granular control over user permissions and commands.
  • RADIUS is a good choice for environments where there is a mix of Cisco and non-Cisco devices, or where extensive accounting features are required.

Τhe choice between RADIUS and TACACS+ largely depends on the specific requirements of the network environment, such as the level of security needed, the granularity of control required, and the types of devices used within the network.