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CISSP Practice Question: Implement 802.1X authentication on their wired…
A company wants to implement 802.1X authentication on their wired network. Which components are required?
⚠ Common exam trap
Test-takers frequently assume the authenticator (switch) performs the actual authentication, leading them to pick Option B, but in 802.1X the authenticator only controls port state and relays messages—it never validates credentials itself.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Supplicant, authenticator, and authentication server
802.1X requires three distinct roles to function: the supplicant (client software requesting access), the authenticator (network device like a switch that enforces port-based access control), and the authentication server (typically a RADIUS server that validates credentials). Without all three, the EAP (Extensible Authentication Protocol) exchange cannot complete, as the authenticator acts as a proxy between the supplicant and the authentication server. Option C is correct because it lists all three mandatory components.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Supplicant and authenticator
Why it's wrong here
This option is incorrect because while the supplicant (client device) attempts to gain network access and the authenticator (network device like a switch or AP) controls port access, the crucial authentication server is missing. Without a centralized authentication server, such as a RADIUS server, the authenticator lacks the necessary database and logic to verify the supplicant's credentials and make an informed access decision, rendering the 802.1X process incomplete and ineffective.
- ✗
Authenticator and authentication server
Why it's wrong here
This option is incorrect because it omits the supplicant, which is the end-user device or client attempting to connect to the network. Although the authenticator (e.g., a switch) and the authentication server (e.g., a RADIUS server) are present and ready to perform their roles, there is no entity initiating the authentication request. The 802.1X protocol cannot function without a client device actively seeking network access and providing credentials to be verified.
- ✓
Supplicant, authenticator, and authentication server
Why this is correct
This option is correct because all three components are absolutely essential for a functional 802.1X implementation. The supplicant (the client device) initiates the authentication process, the authenticator (the network access device like a switch or wireless AP) acts as a gatekeeper, relaying authentication messages and enforcing access policies, and the authentication server (typically a RADIUS server) validates the supplicant's credentials against its database and informs the authenticator of the access decision.
- ✗
Supplicant and authentication server
Why it's wrong here
This option is incorrect because it omits the authenticator, which is the critical intermediary network device (e.g., an Ethernet switch or wireless access point) that controls physical or logical port access. The supplicant (client) cannot directly communicate its authentication requests to the authentication server; it requires the authenticator to relay these messages and enforce the server's access decisions. Without the authenticator, there is no mechanism to block unauthorized access at the network edge or to facilitate the EAP exchange.
Quick reference
AAA Protocol Comparison
| Protocol | Port(s) | Encryption | Transport | Primary Use |
|---|---|---|---|---|
| RADIUS | 1812 / 1813 | Password only | UDP | Network access control |
| TACACS+ | 49 | Full packet | TCP | Device administration |
| Diameter | 3868 | Full session | TCP / SCTP | Carrier / mobile networks |
| 802.1X | — | EAP-based | Layer 2 | Port-based access control |
TACACS+ encrypts the entire packet; RADIUS only encrypts the password field — a key exam distinction.
Go deeper
Related to this question
Learn chapter
Secure Network Architecture and Components
Key term
RADIUS
RADIUS is a network protocol that provides centralized authentication, authorization, and accounting management for users who connect and use a network service.
Key term
Authentication
Authentication is the process of verifying that someone or something is who or what it claims to be before granting access to a system or resource.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISSP practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISSP exam.