The answer is 802.1X, the port-based network access control technology that authenticates users and devices before granting network access, regardless of the physical port they connect to. This works because 802.1X uses the Extensible Authentication Protocol over LAN (EAPoL) to communicate with a central RADIUS server, which verifies credentials and dynamically opens or blocks the switch port, ensuring only authenticated endpoints gain entry. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of how 802.1X enforces security at the port level, independent of the user’s location—a common trap is confusing it with MAC filtering, which only checks hardware addresses without true authentication. Remember the key players: the supplicant (client), authenticator (switch), and authentication server (RADIUS). For a quick memory tip, think “1X = one port, one login”—each port requires a separate authentication, making it ideal for dynamic, secure access control.
N10-009 Network Security Practice Question
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 security auditor recommends implementing a solution that authenticates users and devices before granting network access, regardless of the physical port they connect to. Which technology should be deployed?
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 technology because it provides port-based network access control (PNAC) that authenticates users and devices before granting network access, regardless of the physical port they connect to. It uses the Extensible Authentication Protocol (EAP) over LAN (EAPoL) to communicate with a RADIUS server, ensuring that only authenticated endpoints are allowed on the network. This meets the auditor's requirement for authentication at the port level, independent of the switch port used.
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.
✗
Port security
Why it's wrong here
Port security limits the number of MAC addresses allowed on a port but does not authenticate users or devices.
✓
802.1X
Why this is correct
802.1X provides port-based authentication using EAP and requires credentials from the device or user.
Related concept
Read the scenario before looking for a memorised answer.
✗
VLAN hopping
Why it's wrong here
VLAN hopping is an attack technique, not a security control.
✗
DHCP snooping
Why it's wrong here
DHCP snooping filters DHCP messages and prevents rogue DHCP servers, but does not authenticate devices.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse port security with 802.1X because both control port access, but port security only filters by MAC address and does not provide user authentication or integration with a central authentication server, which is the key requirement in the question.
Detailed technical explanation
How to think about this question
802.1X operates in three roles: supplicant (client), authenticator (switch/AP), and authentication server (RADIUS). The authenticator initially places the port in an unauthorized state, allowing only EAPoL traffic; only after successful authentication does the port transition to an authorized state, dynamically assigning the client to a specific VLAN or ACL. In real-world deployments, 802.1X is often combined with MAC Authentication Bypass (MAB) for devices that do not support 802.1X, such as printers or IoT sensors, to maintain security without breaking legacy device connectivity.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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 technology because it provides port-based network access control (PNAC) that authenticates users and devices before granting network access, regardless of the physical port they connect to. It uses the Extensible Authentication Protocol (EAP) over LAN (EAPoL) to communicate with a RADIUS server, ensuring that only authenticated endpoints are allowed on the network. This meets the auditor's requirement for authentication at the port level, independent of the switch port used.
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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which of the following security mechanisms requires a user to authenticate before gaining access to the wired network at a switch port?
easy
✓ A.802.1X
B.Port security
C.ACL
D.MAC authentication
Why A: 802.1X is a port-based Network Access Control (NAC) standard (IEEE 802.1X) that requires a user or device to authenticate via an authentication server (e.g., RADIUS) before the switch port transitions from an unauthorized to an authorized state, allowing full network access. It uses Extensible Authentication Protocol (EAP) over LAN (EAPoL) to carry authentication messages between the supplicant (client), authenticator (switch), and authentication server. This ensures that only authenticated users can access the wired network at the switch port level.
Variation 2. A company wants to ensure that only authorized employee computers can connect to the wired network. Each computer must be authenticated before it is granted access to the network. Which technology is designed to provide this port-based authentication?
easy
✓ A.802.1X
B.WPA2
C.MAC filtering
D.VPN
Why A: 802.1X is the IEEE standard for port-based Network Access Control (NAC). It uses the Extensible Authentication Protocol (EAP) over LAN (EAPoL) to authenticate a device at the switch port before granting full network access. Only after successful authentication does the switch open the port, ensuring that unauthorized computers cannot connect.
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Question Discussion
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