The correct approach is to place each tier in a separate subnet with appropriate security group rules controlling traffic. This design works because security groups act as stateful, instance-level virtual firewalls at the hypervisor layer, allowing you to specify inbound rules that restrict the application tier to only accept traffic from the web tier’s security group, and the database tier to only accept traffic from the application tier’s security group. On the CompTIA Cloud+ CV0-004 exam, this scenario tests your understanding of the three-tier VPC network architecture design and the principle of least privilege—a common trap is confusing network ACLs (stateless, subnet-level) with security groups (stateful, instance-level). Remember that security groups support referencing other security groups as sources, which is the key to chaining access between tiers. A helpful memory tip: “SG chains for tier lanes”—security groups chain together to create isolated lanes for web, app, and database tiers.
CV0-004 Operations and Support Practice Question
This CV0-004 practice question tests your understanding of operations and support. 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 cloud administrator is configuring a new virtual private cloud (VPC) for a three-tier application. The web tier must be accessible from the internet, the application tier should only be accessible from the web tier, and the database tier should only be accessible from the application tier. Which network architecture should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Place each tier in a separate subnet with appropriate security group rules controlling traffic.
Option C is correct because placing each tier in a separate subnet and using security group rules provides stateful, instance-level traffic control. Security groups act as virtual firewalls at the hypervisor layer, allowing you to specify inbound rules that restrict the application tier to only accept traffic from the web tier's security group, and the database tier to only accept traffic from the application tier's security group. This aligns with the principle of least privilege and ensures that each tier is isolated within the VPC while maintaining necessary connectivity.
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.
✗
Use one subnet with network ACLs to restrict traffic between tiers.
Why it's wrong here
NACLs are stateless and more complex to manage; separate subnets with security groups are preferred.
✗
Place all tiers in the same subnet and use host-based firewalls.
Why it's wrong here
Same subnet lacks network isolation; host firewalls add complexity and may not be sufficient.
✓
Place each tier in a separate subnet with appropriate security group rules controlling traffic.
Why this is correct
Correct. Separate subnets with security groups allow granular control and align with security best practices.
Related concept
Read the scenario before looking for a memorised answer.
✗
Deploy each tier in a different VPC and peer them.
Why it's wrong here
VPC peering adds latency and management overhead; internal subnet segmentation is simpler.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse network ACLs (stateless, subnet-level) with security groups (stateful, instance-level) and assume a single subnet with ACLs can achieve the same isolation, but ACLs cannot filter based on source security group IDs and require manual IP management, making them unsuitable for this multi-tier access control requirement.
Detailed technical explanation
How to think about this question
Security groups are stateful, meaning that if you allow inbound traffic from the web tier to the application tier, the return traffic is automatically allowed regardless of outbound rules. Under the hood, security group rules are evaluated at the elastic network interface (ENI) level, and you can reference other security groups as sources or destinations, enabling micro-segmentation without managing IP addresses. In a real-world scenario, if the web tier is behind an Application Load Balancer, you would attach the web tier's security group to the ALB and then allow the application tier's security group to accept traffic only from that ALB's security group, ensuring that no direct internet traffic reaches the application tier.
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 administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Operations and Support — This question tests Operations and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Place each tier in a separate subnet with appropriate security group rules controlling traffic. — Option C is correct because placing each tier in a separate subnet and using security group rules provides stateful, instance-level traffic control. Security groups act as virtual firewalls at the hypervisor layer, allowing you to specify inbound rules that restrict the application tier to only accept traffic from the web tier's security group, and the database tier to only accept traffic from the application tier's security group. This aligns with the principle of least privilege and ensures that each tier is isolated within the VPC while maintaining necessary connectivity.
What should I do if I get this CV0-004 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.
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Question Discussion
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