The answer is port security, because it allows a network administrator to statically bind a specific MAC address to a switch port, ensuring only that known laptop can connect. When configured, the switch examines the source MAC of every incoming frame; if it does not match the allowed address, the port either drops the traffic or enters an error-disabled state, effectively blocking unauthorized devices. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of layer 2 access control, often appearing alongside questions about MAC flooding attacks or DHCP snooping. A common trap is confusing port security with 802.1X, but remember: port security is a static, port-level restriction based on MAC addresses, while 802.1X uses authentication. For a quick memory tip, think “port security locks the port to one MAC,” or use the mnemonic “P.S. I locked the door” to recall that Port Security is the feature for physically restricting a port to a single device.
N10-009 Network Security Practice Question
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 ensure that only a specific laptop can connect to a particular switch port. The laptop's MAC address is known. Which security feature should be configured?
Why wrong: 802.1X requires authentication via a RADIUS server, but it does not rely on a static list of MAC addresses. It is not the best choice for simply restricting access by MAC address.
B
Port security
Port security allows the administrator to configure allowed MAC addresses per port, limiting access to specific devices. This directly meets the requirement.
C
DHCP snooping
Why wrong: DHCP snooping is used to filter DHCP messages and protect against rogue DHCP servers, not to restrict which device can connect to a switch port.
D
BPDU guard
Why wrong: BPDU guard disables ports that receive Spanning Tree Protocol BPDUs, preventing loops, but it does not control which end devices can connect.
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 statically configure the allowed MAC address on a specific switch port. Once configured, the switch will only forward traffic from that MAC address, dropping frames from any other source MAC. This directly fulfills the requirement to restrict access to a single known laptop.
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.
✗
802.1X
Why it's wrong here
802.1X requires authentication via a RADIUS server, but it does not rely on a static list of MAC addresses. It is not the best choice for simply restricting access by MAC address.
✓
Port security
Why this is correct
Port security allows the administrator to configure allowed MAC addresses per port, limiting access to specific devices. This directly meets the requirement.
Related concept
Read the scenario before looking for a memorised answer.
✗
DHCP snooping
Why it's wrong here
DHCP snooping is used to filter DHCP messages and protect against rogue DHCP servers, not to restrict which device can connect to a switch port.
✗
BPDU guard
Why it's wrong here
BPDU guard disables ports that receive Spanning Tree Protocol BPDUs, preventing loops, but it does not control which end devices can connect.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between port security (which controls MAC-level access on a single port) and 802.1X (which controls network access via authentication), leading candidates to mistakenly choose 802.1X because they associate it with 'security' and 'laptop access' without understanding the specific requirement of a static MAC binding.
Detailed technical explanation
How to think about this question
Under the hood, port security uses a secure MAC address table on the switch interface. When configured with the 'switchport port-security mac-address <MAC>' command, the switch adds a static entry for that MAC in the CAM table and will not learn any other MAC on that port. If a violation occurs (e.g., a different MAC tries to send frames), the switch can be configured to shut down the port, restrict traffic, or protect by dropping frames, depending on the violation mode. In a real-world scenario, this is often used in conjunction with sticky MAC learning to dynamically record the first MAC seen and then lock the port.
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 statically configure the allowed MAC address on a specific switch port. Once configured, the switch will only forward traffic from that MAC address, dropping frames from any other source MAC. This directly fulfills the requirement to restrict access to a single known laptop.
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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