Question 144 of 464
802.1X Network Access Control
A company wants to implement network access control that requires users to authenticate before gaining access to the network. The NAC solution uses a policy that checks for antivirus updates and OS patches. Which component enforces the policy?
Quick Answer
The key to this question is separating the roles inside an 802.1X-based NAC deployment: the supplicant is the device requesting access, the authentication server evaluates credentials and policy compliance, and the authenticator is the device sitting in between that actually controls the port or SSID state. Even though the antivirus and patch checks are evaluated by the authentication server's policy logic, that server doesn't have a physical connection to enforce anything - it only returns a decision. The authenticator, typically the switch or wireless access point, is the one that receives that decision and acts on it, whether that means fully opening the port, denying it outright, or placing the device into a restricted or quarantine VLAN until it becomes compliant. This split between deciding and enforcing is a common source of confusion, since it's easy to assume whichever component runs the compliance check is also the one that blocks access. Whenever a question describes a policy being evaluated versus a policy being applied to a port or connection, remember that evaluation belongs to the authentication server while enforcement belongs to the authenticator - and if the question specifically asks who enforces the outcome, the answer is the authenticator every time.
⚠ Common exam trap
It's easy for candidates to confuse the Authentication Server (which makes the decision) with the Authenticator (which enforces the decision), especially when the question emphasizes 'policy checks' like antivirus updates, leading them to incorrectly select the server.
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
✓
Authenticator
The Authenticator (typically a switch or wireless access point) is the component that enforces the NAC policy by controlling access to the network port or SSID. It receives the authentication result from the Authentication Server and applies the policy (e.g., placing the endpoint in a quarantine VLAN if antivirus or OS patch checks fail). This enforcement is defined in IEEE 802.1X, where the Authenticator acts as the gatekeeper between the Supplicant and the network.
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
Why it's wrong here
The supplicant is the client software on the user’s device that requests access, it does not enforce policy.
When this WOULD be correct
In a question asking 'Which component requests network access and provides credentials?', the supplicant would be correct, as it is the client-side entity that initiates authentication.
- ✓
Authenticator
Why this is correct
The authenticator (e.g., a switch) enforces the policy by controlling the port state based on the authentication result.
- ✗
Authentication server
Why it's wrong here
The authentication server (e.g., RADIUS) validates credentials and sends authorization instructions, but enforcement is done by the authenticator.
When this WOULD be correct
In a scenario where the question asks which component stores and evaluates the access policies (e.g., 'Which component defines the rules for network access?'), the authentication server or policy server would be correct.
- ✗
Policy server
Why it's wrong here
The policy server defines and manages policies, but does not enforce them at the network level.
When this WOULD be correct
A question asking 'Which component stores and manages the NAC policies?' or 'Which component defines the access rules based on endpoint compliance?' would make the policy server the correct answer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓AuthenticatorCorrect answer▾
Why this is correct
The authenticator (e.g., a switch) enforces the policy by controlling the port state based on the authentication result.
✗SupplicantWrong answer — click to see why▾
Why this is wrong here
The supplicant is the client software that requests access, not the component that enforces the policy. Enforcement is done by the authenticator (e.g., switch or wireless controller) which applies the policy after authentication.
★ When this WOULD be the correct answer
In a question asking 'Which component requests network access and provides credentials?', the supplicant would be correct, as it is the client-side entity that initiates authentication.
Why candidates choose this
Candidates may confuse the supplicant's role in authentication with policy enforcement, thinking the client-side software enforces the checks, when in fact it only reports its status.
✗Authentication serverWrong answer — click to see why▾
Why this is wrong here
The authentication server (e.g., RADIUS) validates credentials and checks policy compliance but does not enforce the policy by controlling network access; enforcement is done by the authenticator (e.g., switch or wireless controller) that applies the result.
★ When this WOULD be the correct answer
In a scenario where the question asks which component stores and evaluates the access policies (e.g., 'Which component defines the rules for network access?'), the authentication server or policy server would be correct.
Why candidates choose this
Candidates often confuse the authentication server's role in validating credentials and policies with the enforcement action, assuming the server that checks compliance also enforces access.
✗Policy serverWrong answer — click to see why▾
Why this is wrong here
The policy server defines and stores policies but does not enforce them; enforcement is done by the authenticator (e.g., switch or wireless controller) that applies the policy to the endpoint.
★ When this WOULD be the correct answer
A question asking 'Which component stores and manages the NAC policies?' or 'Which component defines the access rules based on endpoint compliance?' would make the policy server the correct answer.
Why candidates choose this
Candidates confuse the role of the policy server with enforcement because the term 'policy' implies control, leading them to think it enforces the rules it defines.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
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.
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Same concept, more angles
2 more ways this is tested on N10-009
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is implementing network access control to ensure only authenticated users can connect to the wired network. Users must authenticate using their domain credentials before gaining full network access. Which standard should be implemented?
medium- ✓ A.802.1X
- B.802.3af
- C.802.11i
- D.802.1Q
Why A: 802.1X is the IEEE standard for port-based network access control (PNAC). It uses the Extensible Authentication Protocol (EAP) to authenticate devices attempting to connect to a wired or wireless LAN, requiring valid domain credentials before the switch port grants full network access.
Variation 2. A company wants to enforce network access control such that only authenticated users can connect to the wired network. The authentication server will use RADIUS. Which IEEE standard should be implemented?
medium- A.802.11i
- ✓ B.802.1X
- C.802.3af
- D.802.1Q
Why B: 802.1X is the IEEE standard for port-based network access control (PNAC). It provides a framework for authenticating devices before granting access to a wired or wireless LAN, using an authentication server such as RADIUS. This directly meets the requirement to enforce network access control so that only authenticated users can connect to the wired network.
Last reviewed: Jun 11, 2026
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