Quick Answer
The correct answer is supplicant, authenticator, and authentication server. These three components are mandatory because 802.1X authentication relies on the Extensible Authentication Protocol (EAP) exchange, where the supplicant (client software) requests access, the authenticator (a switch or wireless access point) enforces port-based control by blocking traffic until authentication succeeds, and the authentication server (typically a RADIUS server) validates the credentials. Without any one of these roles, the EAP handshake cannot complete, as the authenticator acts solely as a proxy between the supplicant and the server. On the CISSP exam, this question tests your understanding of network access control fundamentals—a common trap is omitting the authenticator or confusing it with the server. Remember the mnemonic “SAS” for Supplicant, Authenticator, Server: all three must be present for the lock to open.
This CISSP practice question tests your understanding of communication and network security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company wants to implement 802.1X authentication on their wired network. Which components are required?
Supplicant and authenticator
Why wrong: Missing the authentication server.
Authenticator and authentication server
Why wrong: Missing the supplicant.
Supplicant, authenticator, and authentication server
All three components are required for 802.1X.
Supplicant and authentication server
Why wrong: Missing the authenticator.
Answer choices
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
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
Missing the authentication server.
Authenticator and authentication server
Why it's wrong here
Missing the supplicant.
Supplicant, authenticator, and authentication server
Why this is correct
All three components are required for 802.1X.
Related concept
Read the scenario before looking for a memorised answer.
Supplicant and authentication server
Why it's wrong here
Missing the authenticator.
Common exam traps
The trap here is that candidates often 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.
Detailed technical explanation
Under the hood, 802.1X uses EAP over LAN (EAPoL) between the supplicant and authenticator, and RADIUS (RFC 2865) between the authenticator and authentication server. The authenticator operates in a 'pass-through' mode, encapsulating EAP messages into RADIUS packets without inspecting the inner authentication method. A real-world scenario: if the authentication server is unreachable, the authenticator may apply a 'fail-open' or 'fail-closed' policy, which can inadvertently grant access to unauthorized devices or block legitimate users.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
What to study next
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FAQ
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
The correct answer is: 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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.
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