N10-005 Question #409: Real Exam Question with Answer & Explanation

The correct answer is C: RADIUS. RADIUS (Remote Authentication Dial-In User Service) is the most likely service because it supports both UDP (traditionally ports 1812/1645 for authentication, 1813/1646 for accounting) and TCP (via RadSec, RFC 6613). RADIUS is the standard AAA protocol used to authenticate VPN us

Question

A technician has configured a router to authenticate VPN users to an LDAP server on the network. In order to allow the authentication service, both UDP and TCP ports needed to be allowed on the router. Which of the following services was MOST likely used?

Options

AKerberos
BTACACS+
CRADIUS
D802.1x

Explanation

RADIUS (Remote Authentication Dial-In User Service) is the most likely service because it supports both UDP (traditionally ports 1812/1645 for authentication, 1813/1646 for accounting) and TCP (via RadSec, RFC 6613). RADIUS is the standard AAA protocol used to authenticate VPN users and can proxy credentials to a backend LDAP server. Kerberos uses TCP/UDP port 88 but is not typically used in this VPN-to-LDAP flow. TACACS+ uses only TCP port 49. 802.1X is a framework, not a standalone AAA service.

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