This CC 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 small company has a single flat network with no segmentation. They recently experienced a malware outbreak that spread quickly across all devices. The IT manager wants to implement network segmentation to contain future outbreaks with minimal cost and complexity. The company currently has a single switch and a router/firewall appliance. The network consists of three departments: Sales, HR, and Engineering. After analyzing the requirements, what is the best course of action?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Replace the single switch with multiple managed switches and create VLANs for each department, then connect them to the firewall
Option B is correct because VLANs logically segment the flat network into separate broadcast domains for Sales, HR, and Engineering, containing malware spread at Layer 2. Using multiple managed switches with VLANs and trunking to the firewall allows inter-VLAN traffic to be inspected and controlled by the firewall, providing segmentation with minimal cost and complexity. This approach leverages existing hardware (router/firewall) and avoids the expense of additional appliances.
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.
✗
Deploy a next-generation firewall between the switch and the router to inspect traffic
Why it's wrong here
This adds perimeter security but does not segment the internal network.
✓
Replace the single switch with multiple managed switches and create VLANs for each department, then connect them to the firewall
Why this is correct
This provides logical segmentation using VLANs, containing outbreaks.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Implement 802.1X authentication on the switch to control device access
Why it's wrong here
802.1X authenticates devices but does not segment traffic between departments.
✗
Install host-based firewalls on all endpoints
Why it's wrong here
Host firewalls protect individual devices but do not prevent lateral movement across the network.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the misconception that adding a firewall or security appliance alone provides segmentation, when in fact segmentation requires separating Layer 2 broadcast domains (via VLANs or physical separation) before applying access controls.
Detailed technical explanation
How to think about this question
VLANs operate at Layer 2 by tagging Ethernet frames with 802.1Q headers, isolating broadcast domains and preventing direct communication between VLANs without a Layer 3 device. The router/firewall performs inter-VLAN routing (router-on-a-stick) using subinterfaces, allowing ACLs or firewall rules to filter traffic between departments. In a real-world scenario, if Engineering’s VLAN is compromised, the firewall can block all traffic from that VLAN to HR and Sales, containing the outbreak while maintaining necessary access.
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 SOC analyst notices unusual lateral movement in the network at 2 AM. The IR playbook dictates: identify and contain (isolate the affected machine), then eradicate (remove the malware), then recover (restore from backup), then document. Skipping containment before eradication risks the attacker regaining access. Questions like this test the sequence and rationale of incident response phases.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CC 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: Replace the single switch with multiple managed switches and create VLANs for each department, then connect them to the firewall — Option B is correct because VLANs logically segment the flat network into separate broadcast domains for Sales, HR, and Engineering, containing malware spread at Layer 2. Using multiple managed switches with VLANs and trunking to the firewall allows inter-VLAN traffic to be inspected and controlled by the firewall, providing segmentation with minimal cost and complexity. This approach leverages existing hardware (router/firewall) and avoids the expense of additional appliances.
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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