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Difficulty: MediumAAA Framework and Authentication Methods

A network administrator is evaluating central authentication services for an enterprise network to support both remote access users and administrative switch management. Which of the following characteristics accurately describe operational differences between the RADIUS and TACACS+ protocols? (Select TWO).

  1. RADIUS encrypts only the password field within packets, whereas TACACS+ encrypts the entire packet body after the header.Answer
  2. B
    TACACS+ combines authentication and authorization into a single protocol exchange, whereas RADIUS completely separates all three AAA services.
  3. TACACS+ operates over TCP port 49, whereas standard RADIUS authentication traffic operates over UDP port 1812.Answer
  4. D
    RADIUS uses TCP port 49 for administrative authentication, whereas TACACS+ utilizes UDP port 1813 for session logging.

Answer

The correct statements indicate that RADIUS encrypts only the password field while TACACS+ encrypts the entire payload body, and that TACACS+ operates over TCP port 49 while standard RADIUS authentication uses UDP port 1812.
The correct options accurately identify protocol characteristics: RADIUS encrypts solely the password field using a shared secret and MD5 stream cipher, whereas TACACS+ encrypts the entire packet body following the header. Furthermore, TACACS+ uses TCP port 49 for connection-oriented transport, while RADIUS uses UDP port 1812 for authentication and UDP port 1813 for accounting.

Step-by-Step Solution

1
Analyze encryption coverage differences between RADIUS and TACACS+.
RADIUS encrypts only the user password field within Access-Request attributes. TACACS+ encrypts the full payload of every packet following the header, providing stronger overall confidentiality.
Security protocol differentiation is key to matching requirements for Administrative AAA vs Network Access AAA.
2
Analyze transport protocol and port assignments for both AAA protocols.
TACACS+ uses TCP port 49 for reliable packet delivery. RADIUS uses UDP ports 1812 (authentication/authorization) and 1813 (accounting).
Identifying transport layer protocols (TCP vs UDP) and standard port numbers is necessary for firewall rule configuration and protocol identification.
3
Evaluate AAA service coupling characteristics.
RADIUS combines authentication and authorization into single attribute exchanges (Access-Request / Access-Accept), whereas TACACS+ strictly separates AAA functions into independent processes.
This modularity allows TACACS+ to enforce per-command authorization on network devices, which RADIUS cannot natively achieve.

Key Concept

RADIUS vs TACACS+ Protocol Architecture and Operational Differences
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Topics

AAA Framework and Authentication Methods

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