- A
Enable VPC flow logs to detect and block malicious traffic.
Why wrong: VPC flow logs capture IP traffic information for analysis but do not actively block or filter traffic.
- B
Configure a security group with inbound rules for the web tier and outbound rules for the database tier.
Why wrong: Security groups are stateful and cannot filter traffic between subnets; they are attached to instances and apply to all traffic to that instance.
- C
Create an IAM policy to restrict access between subnets.
Why wrong: IAM policies control permissions for users and services, not network traffic routing or filtering.
- D
Implement network ACLs with rules that allow only HTTP/HTTPS from web to database and block all other traffic.
Network ACLs are stateless and can be used to filter traffic between subnets at the VPC subnet boundary, with explicit allow/deny rules.
CV0-004 Security Practice Question
This CV0-004 practice question tests your understanding of 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 cloud administrator is configuring a new virtual private cloud (VPC) and needs to ensure that traffic between web servers and database servers is restricted to only the necessary ports. Which security approach should the administrator implement?
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
Implement network ACLs with rules that allow only HTTP/HTTPS from web to database and block all other traffic.
Network ACLs provide stateless filtering at the subnet level, allowing explicit allow/deny rules for inbound and outbound traffic. Security groups are stateful and operate at the instance level, but they are not as effective for subnet-level segmentation. IAM roles manage permissions for services, not traffic filtering. Flow logs capture traffic information but do not restrict it.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable VPC flow logs to detect and block malicious traffic.
Why it's wrong here
VPC flow logs capture IP traffic information for analysis but do not actively block or filter traffic.
- ✗
Configure a security group with inbound rules for the web tier and outbound rules for the database tier.
Why it's wrong here
Security groups are stateful and cannot filter traffic between subnets; they are attached to instances and apply to all traffic to that instance.
- ✗
Create an IAM policy to restrict access between subnets.
Why it's wrong here
IAM policies control permissions for users and services, not network traffic routing or filtering.
- ✓
Implement network ACLs with rules that allow only HTTP/HTTPS from web to database and block all other traffic.
Why this is correct
Network ACLs are stateless and can be used to filter traffic between subnets at the VPC subnet boundary, with explicit allow/deny rules.
Related concept
CIDR notation defines the prefix length.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related CV0-004 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this CV0-004 question test?
Security — This question tests Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Implement network ACLs with rules that allow only HTTP/HTTPS from web to database and block all other traffic. — Network ACLs provide stateless filtering at the subnet level, allowing explicit allow/deny rules for inbound and outbound traffic. Security groups are stateful and operate at the instance level, but they are not as effective for subnet-level segmentation. IAM roles manage permissions for services, not traffic filtering. Flow logs capture traffic information but do not restrict it.
What should I do if I get this CV0-004 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related CV0-004 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 24, 2026
This CV0-004 practice question is part of Courseiva's free CompTIA 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 CV0-004 exam.
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