Network Access Control (NAC) is the correct choice because it enforces security policies by inspecting device health—such as updated antivirus definitions and OS patches—before granting network access, and it works across both wired and wireless connections. This directly meets the requirement to allow only authorized, policy-compliant devices onto the internal network. On the CompTIA Network+ N10-009 exam, NAC questions often test your understanding of pre-admission enforcement versus post-admission controls, with a common trap being to confuse NAC with a firewall or an intrusion prevention system, which do not perform endpoint compliance checks. Remember that NAC is the gatekeeper that checks your device’s “vaccination card” before letting it in, while a firewall only controls traffic after the device is already connected. A useful memory tip: NAC stands for “No Access without Compliance.”
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 ensure that only authorized devices that comply with security policies (such as updated antivirus and OS patches) are allowed to connect to the internal network. Both wired and wireless connections are used. Which of the following security solutions would best enforce this requirement?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Why wrong: A VPN encrypts traffic between a client and network but does not enforce device compliance policies. It assumes the device is already trusted.
B
Network Access Control (NAC)
NAC solutions like Cisco ISE or Aruba ClearPass can enforce security policies by scanning endpoints before allowing access and quarantining non-compliant devices.
C
Access control list (ACL)
Why wrong: ACLs filter traffic based on packet attributes but do not evaluate device health or compliance. They are stateless and cannot enforce pre-admission policies.
D
Intrusion prevention system (IPS)
Why wrong: An IPS monitors and blocks malicious traffic but does not perform endpoint compliance checks before granting network access.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Network Access Control (NAC)
Network Access Control (NAC) is the correct solution because it enforces security policies by inspecting the health and compliance of devices—such as checking for updated antivirus definitions and OS patches—before granting access to the network. NAC can operate on both wired (e.g., 802.1X) and wireless (e.g., WPA2-Enterprise with RADIUS) connections, blocking or quarantining non-compliant devices. This matches the requirement to ensure only authorized, policy-compliant devices connect.
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.
✗
VPN
Why it's wrong here
A VPN encrypts traffic between a client and network but does not enforce device compliance policies. It assumes the device is already trusted.
✓
Network Access Control (NAC)
Why this is correct
NAC solutions like Cisco ISE or Aruba ClearPass can enforce security policies by scanning endpoints before allowing access and quarantining non-compliant devices.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Access control list (ACL)
Why it's wrong here
ACLs filter traffic based on packet attributes but do not evaluate device health or compliance. They are stateless and cannot enforce pre-admission policies.
✗
Intrusion prevention system (IPS)
Why it's wrong here
An IPS monitors and blocks malicious traffic but does not perform endpoint compliance checks before granting network access.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse NAC with VPN or ACL, thinking VPN provides endpoint security or ACLs can enforce policy compliance, but NAC is the only solution that performs dynamic, policy-based admission control based on device health and authorization.
Detailed technical explanation
How to think about this question
NAC typically uses the 802.1X standard with EAP (e.g., EAP-TLS or PEAP) and a RADIUS server (like Cisco ISE or Aruba ClearPass) to authenticate and assess device posture via agents or passive scanning. Posture validation can involve checking registry keys, file versions, or running processes (e.g., verifying antivirus definitions via OPSWAT or custom scripts), and non-compliant devices are placed into a quarantine VLAN with restricted access. In real-world deployments, NAC can also integrate with MDM solutions to enforce policies on mobile devices, and it supports pre-admission and post-admission controls to continuously monitor compliance.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: Network Access Control (NAC) — Network Access Control (NAC) is the correct solution because it enforces security policies by inspecting the health and compliance of devices—such as checking for updated antivirus definitions and OS patches—before granting access to the network. NAC can operate on both wired (e.g., 802.1X) and wireless (e.g., WPA2-Enterprise with RADIUS) connections, blocking or quarantining non-compliant devices. This matches the requirement to ensure only authorized, policy-compliant devices connect.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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