Port 1812/TCP, UDP is used for which RADIUS service?

Port 1812/TCP, UDP is used for which RADIUS service?

• A. RADIUS accounting protocol
• B. TACACS+ protocol
• C. RADIUS authentication protocol
• D. Diameter protocol

Answer: (C)

RADIUS uses port 1812 for authentication and authorization. When a network access server (NAS) needs to verify a user, it sends an Access-Request to the RADIUS server on UDP port 1812, and the server replies with Access-Accept, Access-Reject, or Access-Challenge to grant or deny access. The accounting function lives on a different port, typically 1813, so it is not the same as the authentication service. Other protocols like TACACS+ use different ports (49), and Diameter is a separate protocol that usually operates on a different port (and transport). So port 1812 is specifically tied to the RADIUS authentication/authorization process.

RADIUS uses port 1812 for authentication and authorization. When a network access server (NAS) needs to verify a user, it sends an Access-Request to the RADIUS server on UDP port 1812, and the server replies with Access-Accept, Access-Reject, or Access-Challenge to grant or deny access. The accounting function lives on a different port, typically 1813, so it is not the same as the authentication service. Other protocols like TACACS+ use different ports (49), and Diameter is a separate protocol that usually operates on a different port (and transport). So port 1812 is specifically tied to the RADIUS authentication/authorization process.