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 network administrator wants to prevent unauthorized devices from being plugged into switch ports. Only devices with specific MAC addresses should be allowed on each port. Which switch security feature should be enabled?
Why wrong: DHCP snooping filters DHCP messages to prevent rogue DHCP servers, but it does not restrict which MAC addresses can connect to a port.
B
Dynamic ARP inspection
Why wrong: DAI validates ARP packets to prevent ARP spoofing, but it does not control which MAC addresses are allowed on a port.
C
Port security
Correct. Port security limits the MAC addresses that can communicate through a switch port, preventing unauthorized devices from connecting.
D
802.1X
Why wrong: 802.1X provides network access control by authenticating users or devices before granting access, but it relies on a RADIUS server and does not specifically restrict based on MAC addresses alone.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Port security
Port security is the correct feature because it allows the administrator to restrict which MAC addresses can communicate through a switch port. By configuring allowed MAC addresses (sticky or static), any device with an unknown MAC address attempting to send traffic will trigger a security violation (shutdown, restrict, or protect). This directly addresses the requirement to prevent unauthorized devices from being plugged into switch ports.
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.
✗
DHCP snooping
Why it's wrong here
DHCP snooping filters DHCP messages to prevent rogue DHCP servers, but it does not restrict which MAC addresses can connect to a port.
✗
Dynamic ARP inspection
Why it's wrong here
DAI validates ARP packets to prevent ARP spoofing, but it does not control which MAC addresses are allowed on a port.
✓
Port security
Why this is correct
Correct. Port security limits the MAC addresses that can communicate through a switch port, preventing unauthorized devices from connecting.
Related concept
Read the scenario before looking for a memorised answer.
✗
802.1X
Why it's wrong here
802.1X provides network access control by authenticating users or devices before granting access, but it relies on a RADIUS server and does not specifically restrict based on MAC addresses alone.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between port security (MAC-based access control) and 802.1X (authentication-based access control), leading candidates to incorrectly choose 802.1X when the question explicitly mentions 'specific MAC addresses' rather than user credentials or certificates.
Detailed technical explanation
How to think about this question
Port security operates by limiting the number of MAC addresses allowed on a port (default is 1) and can be configured with sticky MAC addresses that dynamically learn and save allowed MACs to the running config. When a violation occurs, the port can be placed in err-disabled state (shutdown mode), which requires manual or automatic recovery via errdisable recovery cause psecure-violation. In real-world scenarios, this is commonly used on access ports in conference rooms or public areas to prevent rogue devices from connecting to the network.
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 practitioner preparing for the N10-009 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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: Port security — Port security is the correct feature because it allows the administrator to restrict which MAC addresses can communicate through a switch port. By configuring allowed MAC addresses (sticky or static), any device with an unknown MAC address attempting to send traffic will trigger a security violation (shutdown, restrict, or protect). This directly addresses the requirement to prevent unauthorized devices from being plugged into switch ports.
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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