- A
Replace the switch with three separate physical switches, each connected to a separate router interface.
Why wrong: This requires new hardware and additional configuration, exceeding the budget constraint.
- B
Create three VLANs on the switch, one for each department, and configure ACLs on the router to allow only necessary inter-VLAN traffic.
VLANs logically separate traffic, and ACLs enforce policy; uses existing hardware if the switch supports VLANs (most do).
- C
Implement MAC address filtering on the switch to only allow authorized devices to communicate with the file server.
Why wrong: MAC filtering does not isolate departments; devices within the same subnet can still communicate.
- D
Install a software firewall on each workstation to block traffic from other subnets.
Why wrong: Host-based firewalls are inconsistent and difficult to manage; they do not prevent all lateral movement.
Quick Answer
The correct answer is to create three VLANs on the switch, one for each department, and configure ACLs on the router to allow only necessary inter-VLAN traffic. This approach directly implements network segmentation with VLANs by dividing the flat /24 subnet into three isolated broadcast domains on the existing single switch, which prevents ransomware from moving laterally between departments by default. The ACLs on the router then act as a firewall between VLANs, permitting only essential traffic—like Sales and HR accessing the IT file server—without requiring any new hardware. On the ISC2 Certified in Cybersecurity CC exam, this scenario tests your understanding of how VLANs enforce segmentation at Layer 2 and how ACLs control inter-VLAN routing at Layer 3, a common trap being to suggest buying a new switch or using separate physical networks, which violates the budget constraint. Remember the mnemonic “VLANs block, ACLs unlock”—VLANs stop the spread, ACLs open only what’s needed.
ISC2 CC Network Security Practice Question
This CC practice question tests your understanding of network security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 with 50 employees uses a flat network with no VLANs. They recently experienced a ransomware attack that spread from an infected workstation to a file server. The IT manager wants to implement network segmentation to prevent future lateral movement. The company uses a single /24 subnet (192.168.1.0/24) with a single switch and a router/firewall. They have three departments: Sales, HR, and IT. Each department has about 15-20 computers. The file server is in the IT department. The company has a limited budget and cannot purchase new hardware. Which of the following is the MOST effective and practical approach to segment the network given these constraints?
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
Create three VLANs on the switch, one for each department, and configure ACLs on the router to allow only necessary inter-VLAN traffic.
Creating three VLANs on the existing switch segments the flat /24 network into separate broadcast domains, preventing lateral movement by default. Configuring ACLs on the router allows only necessary inter-VLAN traffic (e.g., Sales and HR can access the file server in IT), which stops the ransomware from spreading across departments without requiring new hardware.
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.
- ✗
Replace the switch with three separate physical switches, each connected to a separate router interface.
Why it's wrong here
This requires new hardware and additional configuration, exceeding the budget constraint.
- ✓
Create three VLANs on the switch, one for each department, and configure ACLs on the router to allow only necessary inter-VLAN traffic.
Why this is correct
VLANs logically separate traffic, and ACLs enforce policy; uses existing hardware if the switch supports VLANs (most do).
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Implement MAC address filtering on the switch to only allow authorized devices to communicate with the file server.
Why it's wrong here
MAC filtering does not isolate departments; devices within the same subnet can still communicate.
- ✗
Install a software firewall on each workstation to block traffic from other subnets.
Why it's wrong here
Host-based firewalls are inconsistent and difficult to manage; they do not prevent all lateral movement.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the misconception that physical separation (Option A) is always required for segmentation, when in fact VLANs provide logical separation at no extra cost, and that MAC filtering (Option C) or host-based firewalls (Option D) can substitute for network-level segmentation, which they cannot because they fail to isolate broadcast domains or prevent Layer 2 attacks.
Detailed technical explanation
How to think about this question
VLANs operate at Layer 2 by tagging frames with 802.1Q headers, isolating traffic into separate broadcast domains even on a single switch. Inter-VLAN routing requires a Layer 3 device (the router/firewall) to forward traffic between VLANs, and ACLs applied to the router's VLAN interfaces can filter based on source/destination IP and port, providing granular control. In a real-world scenario, this approach is commonly used in small-to-medium businesses to meet segmentation goals without additional hardware, as it leverages the existing switch's VLAN capability and the router's ACL feature.
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
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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: Create three VLANs on the switch, one for each department, and configure ACLs on the router to allow only necessary inter-VLAN traffic. — Creating three VLANs on the existing switch segments the flat /24 network into separate broadcast domains, preventing lateral movement by default. Configuring ACLs on the router allows only necessary inter-VLAN traffic (e.g., Sales and HR can access the file server in IT), which stops the ransomware from spreading across departments without requiring new hardware.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on CC
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 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?
easy- A.Deploy a next-generation firewall between the switch and the router to inspect traffic
- ✓ B.Replace the single switch with multiple managed switches and create VLANs for each department, then connect them to the firewall
- C.Implement 802.1X authentication on the switch to control device access
- D.Install host-based firewalls on all endpoints
Why B: 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.
Last reviewed: Jun 30, 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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