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TACACS Plus Overview and Comparison

Jun 24, 2025

Overview

This lecture covers TACACS Plus, its history, main functions in AAA (Authentication, Authorization, Accounting), and its primary use cases, especially compared to RADIUS.

TACACS Plus Overview

  • TACACS Plus stands for Terminal Access Controller Access Control System Plus.
  • Developed by Cisco and released as an open standard in 1993.
  • TACACS Plus replaced the original TACACS protocol (1984) and XTACACS (Cisco's proprietary extension).
  • Mainly used for device administration AAA, not just network access.

Differences Between TACACS Plus and RADIUS

  • TACACS Plus focuses on device administration, while RADIUS is used mainly for network access.
  • Significant differences exist in authorization and accounting capabilities, not authentication.
  • TACACS Plus separates the authentication, authorization, and accounting (AAA) processes.
  • TACACS Plus is more suitable for securing high-value network infrastructure devices.

Use Cases and Importance

  • TACACS Plus is important for organizations managing critical network devices.
  • Implementation is recommended as organizations grow and security needs increase.
  • Attacks often target network infrastructure, making strong AAA for device access crucial.

Key Terms & Definitions

  • TACACS Plus — An AAA protocol from Cisco for device administration, focusing on authentication, authorization, and accounting.
  • AAA — Authentication, Authorization, and Accounting, the security framework for managing access to network resources.
  • RADIUS — Remote Authentication Dial-In User Service, another AAA protocol mainly used for network access.
  • XTACACS — Cisco's extended version of TACACS, predecessor to TACACS Plus.

Action Items / Next Steps

  • Review the differences between TACACS Plus and RADIUS for network device security.
  • Consider whether TACACS Plus implementation is needed for your organization's infrastructure.