This N10-009 practice question tests your understanding of network security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 connecting to the network by limiting the number of MAC addresses allowed on a switch port. Which security feature should be configured?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
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Port security
Port security is the correct feature because it directly restricts the number of unique MAC addresses that can be learned on a switch port, preventing unauthorized devices from connecting. When the configured limit is exceeded, the switch can take actions such as shutdown, restrict, or protect, effectively blocking the unauthorized device. This is a Layer 2 access control mechanism that operates on the switch port itself.
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.
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802.1X
Why it's wrong here
802.1X provides port-based authentication, but it does not limit the number of MAC addresses per port.
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Port security
Why this is correct
Port security restricts the number of MAC addresses allowed on a port, preventing unauthorized devices from connecting.
Related concept
Read the scenario before looking for a memorised answer.
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DHCP snooping
Why it's wrong here
DHCP snooping protects against rogue DHCP servers but does not limit MAC addresses per port.
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Dynamic ARP inspection
Why it's wrong here
DAI validates ARP packets to prevent spoofing, not to limit MAC addresses.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between port security (MAC address limiting) and 802.1X (authentication), leading candidates to mistakenly choose 802.1X when the question explicitly asks about limiting the number of MAC addresses.
Detailed technical explanation
How to think about this question
Port security uses a sticky MAC address feature that dynamically learns and stores MAC addresses in the running configuration, allowing the administrator to set a maximum (default is 1) per interface. When a violation occurs, the switch can be configured with three violation modes: shutdown (error-disables the port), restrict (drops the frame and increments a counter), or protect (drops the frame silently). In real-world scenarios, this is commonly used on access ports in office environments to prevent unauthorized devices like personal laptops or rogue switches from connecting.
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 directly restricts the number of unique MAC addresses that can be learned on a switch port, preventing unauthorized devices from connecting. When the configured limit is exceeded, the switch can take actions such as shutdown, restrict, or protect, effectively blocking the unauthorized device. This is a Layer 2 access control mechanism that operates on the switch port itself.
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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