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Difficulty: MediumAAA Framework and Authentication Methods

A network administrator is configuring a centralized authentication server to support remote access VPN clients using the RADIUS protocol. Security policies require creating specific firewall rules to permit authentication traffic from the VPN gateway to the backend RADIUS server. Which transport protocol and destination port combination must be allowed through the firewall for standard RADIUS authentication?

  1. UDP port 1812Answer
  2. B
    TCP port 1812
  3. C
    TCP port 49
  4. D
    UDP port 49

Answer

UDP port 1812 is the standard transport protocol and port used for RADIUS authentication.
RADIUS (Remote Authentication Dial-In User Service) is an open-standard AAA protocol that operates over UDP using port 1812 for authentication and authorization, and port 1813 for accounting. Therefore, configuring firewall rules to permit UDP port 1812 allows authentication packets from the VPN gateway to reach the backend server.

Step-by-Step Solution

1
Identify the authentication protocol specified in the scenario.
The scenario specifies RADIUS (Remote Authentication Dial-In User Service).
Determining the target protocol narrows down transport layer requirements.
2
Determine the transport protocol used by RADIUS.
RADIUS uses UDP (User Datagram Protocol).
RADIUS was designed to use lightweight connectionless transport for authentication and accounting frames.
3
Identify the official IANA destination port for RADIUS authentication.
UDP port 1812 is designated for RADIUS authentication messages.
Firewall rules require matching both transport layer protocol and destination port.

Key Concept

RADIUS Port and Transport Layer Protocol Specifications
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Topics

AAA Framework and Authentication Methods

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