802.1X is the correct choice because it provides port-based network access control (PNAC) that requires end devices to authenticate using domain credentials, typically via a RADIUS server, before the switch port fully opens. This ensures that only authorized users—not just any device that physically plugs in—can access the corporate wired network, directly preventing unauthorized personal devices from connecting. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of how 802.1X enforces authentication at the switch port level, often contrasted with MAC address filtering, which only checks device identity and can be spoofed. A common trap is choosing MAC filtering because it seems simpler, but it fails to verify user credentials. Remember the mnemonic: “1X = one user, one login” to distinguish it from device-only controls.
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 company wants to prevent unauthorized personal devices from connecting to the corporate wired network. Employees must authenticate using their domain credentials before gaining full network access. Which security measure should be implemented on the switch ports?
Why wrong: MAC filtering is easy to circumvent by spoofing a legitimate MAC address; it does not verify user identity.
B
802.1X
802.1X uses Extensible Authentication Protocol (EAP) to authenticate devices/users against a central authentication server, enforcing access based on credentials.
C
Port security with sticky MAC
Why wrong: Port security limits the number of MAC addresses per port but does not authenticate users; it can be bypassed by spoofing.
D
VLAN hopping prevention
Why wrong: VLAN hopping prevention (e.g., disabling DTP, using native VLAN tagging) secures trunk links but does not authenticate end devices.
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 choice because it provides port-based network access control (PNAC) that requires end devices to authenticate using domain credentials (e.g., via RADIUS) before being granted full network access. This ensures that only authorized users, not just authorized devices, can connect to the corporate wired network, meeting the requirement to prevent unauthorized personal devices.
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.
✗
MAC filtering
Why it's wrong here
MAC filtering is easy to circumvent by spoofing a legitimate MAC address; it does not verify user identity.
✓
802.1X
Why this is correct
802.1X uses Extensible Authentication Protocol (EAP) to authenticate devices/users against a central authentication server, enforcing access based on credentials.
Related concept
Read the scenario before looking for a memorised answer.
✗
Port security with sticky MAC
Why it's wrong here
Port security limits the number of MAC addresses per port but does not authenticate users; it can be bypassed by spoofing.
✗
VLAN hopping prevention
Why it's wrong here
VLAN hopping prevention (e.g., disabling DTP, using native VLAN tagging) secures trunk links but does not authenticate end 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, thinking that locking MAC addresses via sticky MAC provides user-based authentication, but it only controls device identity, not user credentials, and fails to meet the requirement for domain credential authentication.
Detailed technical explanation
How to think about this question
802.1X operates using the Extensible Authentication Protocol (EAP) over LAN (EAPoL), where the supplicant (client) communicates with the authenticator (switch) and the authentication server (RADIUS) validates domain credentials. In a real-world scenario, if a user connects a personal device that does not support 802.1X (e.g., a legacy printer), the switch can be configured to place that port into a guest VLAN with limited access, while domain-joined devices authenticate seamlessly via PEAP or EAP-TLS.
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 choice because it provides port-based network access control (PNAC) that requires end devices to authenticate using domain credentials (e.g., via RADIUS) before being granted full network access. This ensures that only authorized users, not just authorized devices, can connect to the corporate wired network, meeting the requirement to prevent unauthorized personal devices.
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. A company wants to prevent unauthorized devices from connecting to the wired network by authenticating users or devices before granting network access. Which of the following technologies should be implemented on the switch ports to achieve this?
medium
✓ A.A: 802.1X
B.B: Port security with MAC address sticky
C.C: Access control lists (ACLs)
D.D: DHCP snooping
Why A: 802.1X is an IEEE standard (802.1X-2020) for port-based Network Access Control (NAC). It authenticates users or devices via EAP (Extensible Authentication Protocol) before the switch port transitions from the unauthorized (blocking) state to the authorized (forwarding) state, effectively preventing unauthorized devices from accessing the wired network.
Variation 2. A company wants to ensure that only users who have successfully authenticated Active Directory credentials can access the wired network. The network switches support IEEE 802.1X. Which additional component must be deployed to complete the solution?
hard
✓ A.A RADIUS server
B.A DHCP server
C.A certificate authority
D.A TACACS+ server
Why A: IEEE 802.1X port-based authentication requires a RADIUS server to act as the authentication server. The switch (authenticator) forwards the user's credentials to the RADIUS server, which validates them against Active Directory and returns an accept or reject decision. Without a RADIUS server, the switch has no way to verify the user's credentials against the central identity store.
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Question Discussion
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