Quick Answer
The answer is 802.1X authentication because it enforces port-level security by requiring every device to authenticate before it can access the corporate wired network. This method uses the Extensible Authentication Protocol (EAP) to verify credentials against a central authentication server, effectively blocking unauthorized devices at the switch port. On the ISC2 Certified in Cybersecurity CC exam, this question tests your ability to distinguish between specific technologies and broader concepts: while Network Access Control (NAC) is the overarching framework, 802.1X is the precise mechanism that performs device authentication. A common trap is choosing MAC filtering, which can be easily bypassed by spoofing a permitted address, or VLAN segmentation, which separates traffic but never verifies identity. Remember the memory tip: “1X checks the box” — 802.1X is the one technology that actively checks each device’s credentials before granting network access.
This CC practice question tests your understanding of security principles. 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.
You are implementing a security control to prevent unauthorized devices from connecting to the corporate wired network. Which network access control method should be used?
VLAN segmentation
Why wrong: VLANs separate traffic but do not authenticate devices.
MAC address filtering
Why wrong: MAC addresses can be spoofed, making this control weak.
Network Access Control (NAC) only
Why wrong: NAC is a framework; 802.1X is a specific protocol typically used within NAC.
802.1X authentication
802.1X authenticates devices at the port level, checking credentials before allowing network access.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
802.1X authentication
Option C is correct because 802.1X authentication requires devices to authenticate before gaining network access, providing port-level security. MAC filtering (A) can be bypassed by spoofing. NAC (B) is a broader concept, but 802.1X is the specific technology. VLAN segmentation (D) separates traffic but does not authenticate devices.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
VLAN segmentation
Why it's wrong here
VLANs separate traffic but do not authenticate devices.
MAC address filtering
Why it's wrong here
MAC addresses can be spoofed, making this control weak.
Network Access Control (NAC) only
Why it's wrong here
NAC is a framework; 802.1X is a specific protocol typically used within NAC.
802.1X authentication
Common exam traps
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
A security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
What to study next
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related CC questions on switching, trunking, and access-port configuration.
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FAQ
Security Principles — This question tests Security Principles — Access ports place end devices into a single VLAN..
The correct answer is: 802.1X authentication — Option C is correct because 802.1X authentication requires devices to authenticate before gaining network access, providing port-level security. MAC filtering (A) can be bypassed by spoofing. NAC (B) is a broader concept, but 802.1X is the specific technology. VLAN segmentation (D) separates traffic but does not authenticate devices.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related CC questions on switching, trunking, and access-port configuration.
Access ports place end devices into a single VLAN.
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Last reviewed: Jun 24, 2026
This CC practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CC exam.
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