The answer is the Authenticator. This component enforces the NAC policy by acting as the gatekeeper between the user’s device and the network, typically implemented in a switch or wireless access point. After the Authentication Server verifies credentials and checks compliance conditions like antivirus updates and OS patches, the Authenticator applies the resulting policy—for example, placing a non-compliant device into a quarantine VLAN. On the CompTIA Network+ N10-009 exam, this tests your understanding of the IEEE 802.1X framework, where the Authenticator is the middle component that enforces access decisions. A common trap is confusing the Authenticator with the Authentication Server; remember that the server decides, but the Authenticator enforces. A helpful memory tip: think of the Authenticator as the “bouncer” who checks your ID and then either lets you into the club or sends you to the waiting area.
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 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?
Why wrong: The supplicant is the client software on the user’s device that requests access, it does not enforce policy.
B
Authenticator
The authenticator (e.g., a switch) enforces the policy by controlling the port state based on the authentication result.
C
Authentication server
Why wrong: The authentication server (e.g., RADIUS) validates credentials and sends authorization instructions, but enforcement is done by the authenticator.
D
Policy server
Why wrong: The policy server defines and manages policies, but does not enforce them at the network level.
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
✓
Authenticator
Why this is correct
The authenticator (e.g., a switch) enforces the policy by controlling the port state based on the authentication result.
Related concept
Read the scenario before looking for a memorised answer.
✗
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.
✗
Policy server
Why it's wrong here
The policy server defines and manages policies, but does not enforce them at the network level.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often 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.
Detailed technical explanation
How to think about this question
Under the hood, the Authenticator (switch/AP) uses EAP over LAN (EAPoL) to communicate with the Supplicant and forwards EAP messages to the RADIUS server. After the server evaluates posture via CoA (Change of Authorization) or RADIUS attributes like Filter-ID, the Authenticator dynamically applies a VLAN assignment or ACL to enforce the policy. In a real-world scenario, if the Authenticator fails to enforce, a non-compliant device could bypass quarantine and access sensitive resources, making the Authenticator's role critical.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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