- A
Implement MAC address filtering on the access point to allow only known devices.
Why wrong: MAC filtering does not restrict network-level access; all allowed devices would be on the same network as internal resources.
- B
Connect the guest Wi-Fi to the internet through a separate router that does not have routes to the internal network.
Why wrong: This works but is less efficient and scalable than VLAN segmentation with a single router/firewall.
- C
Use a single VLAN with a DHCP server that assigns different IP ranges to guests and employees.
Why wrong: Devices on the same VLAN can communicate directly regardless of IP range, so internal resources would be reachable.
- D
Place the guest Wi-Fi on a separate VLAN with a firewall rule blocking traffic to internal subnets.
This creates logical isolation and allows granular control over traffic between VLANs.
Quick Answer
The correct answer is to place the guest Wi-Fi on a separate VLAN with a firewall rule blocking traffic to internal subnets. This approach works because the VLAN provides Layer 2 segmentation, logically isolating guest traffic from the corporate network at the switch level, while the firewall ACLs enforce Layer 3 and Layer 4 access control by explicitly denying any traffic destined for internal subnets and only permitting outbound internet access via a default route. On the ISC2 Certified in Cybersecurity CC exam, this question tests your understanding of network segmentation principles and defense-in-depth, often appearing as a scenario where a single solution—like a separate SSID alone—is a trap because it lacks enforcement at the firewall. A common memory tip is to think of the VLAN as the “fence” and the firewall ACL as the “locked gate”; both are needed to keep guests out of the corporate yard. Remember: VLANs isolate, firewalls enforce—never rely on one without the other.
ISC2 CC Network Security Practice Question
This CC practice question tests your understanding of network security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 engineer is designing a network for a small business that needs to segregate guest Wi-Fi from the internal corporate network. The guest network should have internet access only, with no access to internal resources. Which of the following is the BEST design approach?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Place the guest Wi-Fi on a separate VLAN with a firewall rule blocking traffic to internal subnets.
Option D is the best approach because placing the guest Wi-Fi on a separate VLAN and applying a firewall rule to block traffic to internal subnets provides both logical segmentation and access control. This ensures that guest traffic is isolated at Layer 2 (VLAN) and Layer 3/4 (firewall), preventing any unauthorized access to the corporate network while still allowing internet connectivity through a default route.
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.
- ✗
Implement MAC address filtering on the access point to allow only known devices.
Why it's wrong here
MAC filtering does not restrict network-level access; all allowed devices would be on the same network as internal resources.
- ✗
Connect the guest Wi-Fi to the internet through a separate router that does not have routes to the internal network.
- ✗
Use a single VLAN with a DHCP server that assigns different IP ranges to guests and employees.
Why it's wrong here
Devices on the same VLAN can communicate directly regardless of IP range, so internal resources would be reachable.
- ✓
Place the guest Wi-Fi on a separate VLAN with a firewall rule blocking traffic to internal subnets.
Why this is correct
This creates logical isolation and allows granular control over traffic between VLANs.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the misconception that simply using different IP subnets on the same VLAN provides security, when in fact true isolation requires separate VLANs or firewall rules to prevent Layer 2 communication.
Detailed technical explanation
How to think about this question
In practice, VLANs create separate broadcast domains at Layer 2, and when combined with a firewall (or a Layer 3 switch with ACLs), you can enforce policies such as 'deny ip from guest subnet to corporate subnet' while permitting all other traffic. A common real-world implementation uses a Cisco switch with 802.1Q trunking to the access point, where the guest SSID is mapped to a specific VLAN, and the switch or router applies an ACL that blocks RFC 1918 addresses (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) from the guest VLAN, except for the default gateway.
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 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. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this CC question test?
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: Place the guest Wi-Fi on a separate VLAN with a firewall rule blocking traffic to internal subnets. — Option D is the best approach because placing the guest Wi-Fi on a separate VLAN and applying a firewall rule to block traffic to internal subnets provides both logical segmentation and access control. This ensures that guest traffic is isolated at Layer 2 (VLAN) and Layer 3/4 (firewall), preventing any unauthorized access to the corporate network while still allowing internet connectivity through a default route.
What should I do if I get this CC question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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