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 through a switch port. Which security feature should be enabled on the switch?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
802.1X
802.1X is the correct answer because it provides port-based network access control (PNAC) that authenticates devices before granting network access. It uses the Extensible Authentication Protocol (EAP) over LAN (EAPoL) to communicate with a RADIUS server, ensuring only authorized users or devices can connect through the switch port. This prevents unauthorized devices from accessing the network at Layer 2, regardless of MAC address or IP configuration.
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 this is correct
802.1X authenticates devices before allowing them to send traffic, providing strong access control.
Related concept
Read the scenario before looking for a memorised answer.
✗
Port security
Why it's wrong here
Port security restricts the number of allowed MAC addresses but does not authenticate the device; it can be bypassed with MAC spoofing.
✗
MAC filtering
Why it's wrong here
MAC filtering simply allows or denies traffic based on MAC addresses and is not a strong authentication mechanism.
✗
Storm control
Why it's wrong here
Storm control limits broadcast, multicast, or unknown unicast traffic to prevent denial of service, not unauthorized access.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse port security or MAC filtering with true authentication, but Cisco tests that 802.1X is the only feature that performs per-device authentication against a central server, not just static MAC-based controls.
Detailed technical explanation
How to think about this question
802.1X operates in three roles: supplicant (client), authenticator (switch), and authentication server (RADIUS). The switch initially places the port in an unauthorized state, allowing only EAPoL frames; after successful authentication, the port transitions to an authorized state and dynamically opens for user traffic. In real-world deployments, 802.1X is often combined with MAB (MAC Authentication Bypass) for legacy devices that do not support an 802.1X supplicant.
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 junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
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: 802.1X — 802.1X is the correct answer because it provides port-based network access control (PNAC) that authenticates devices before granting network access. It uses the Extensible Authentication Protocol (EAP) over LAN (EAPoL) to communicate with a RADIUS server, ensuring only authorized users or devices can connect through the switch port. This prevents unauthorized devices from accessing the network at Layer 2, regardless of MAC address or IP configuration.
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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