This N10-009 practice question tests your understanding of network security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 prevent unauthorized devices from connecting to the wired network by authenticating users or devices before granting network access. Which of the following technologies should be implemented on the switch ports to achieve this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A: 802.1X
802.1X is an IEEE standard (802.1X-2020) for port-based Network Access Control (NAC). It authenticates users or devices via EAP (Extensible Authentication Protocol) before the switch port transitions from the unauthorized (blocking) state to the authorized (forwarding) state, effectively preventing unauthorized devices from accessing the wired 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.
✓
A: 802.1X
Why this is correct
802.1X provides port-based authentication, blocking access until credentials are verified.
Related concept
Read the scenario before looking for a memorised answer.
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B: Port security with MAC address sticky
Why it's wrong here
Port security limits the number of MAC addresses on a port and can be used to restrict devices, but it does not authenticate users.
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C: Access control lists (ACLs)
Why it's wrong here
ACLs filter traffic based on IP addresses or protocols but do not authenticate before granting network access.
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D: DHCP snooping
Why it's wrong here
DHCP snooping prevents rogue DHCP servers but does not authenticate devices trying to connect to the network.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the misconception that port security with sticky MAC addresses provides authentication, but it only restricts MAC addresses and does not verify user identity or credentials, making it a layer-2 control, not an authentication mechanism.
Detailed technical explanation
How to think about this question
Under the hood, 802.1X uses a supplicant (client), authenticator (switch), and authentication server (typically RADIUS). The switch port starts in the unauthorized state, allowing only EAPoL (EAP over LAN) frames; successful authentication triggers the port to open, often dynamically applying a VLAN or ACL via RADIUS attributes. In real-world deployments, 802.1X is commonly combined with MAB (MAC Authentication Bypass) for devices that lack 802.1X supplicant support, such as printers or IP phones.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
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: A: 802.1X — 802.1X is an IEEE standard (802.1X-2020) for port-based Network Access Control (NAC). It authenticates users or devices via EAP (Extensible Authentication Protocol) before the switch port transitions from the unauthorized (blocking) state to the authorized (forwarding) state, effectively preventing unauthorized devices from accessing the wired 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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