- A
Attach a transit gateway to the VPC and route traffic through it.
Why wrong: Network Firewall can be used without a transit gateway for intra-VPC traffic.
- B
Configure the Network Firewall rule group to allow the desired traffic between subnets.
The firewall must have rules to allow the traffic after routing it through.
- C
Add a route in subnet A's route table that sends traffic to subnet B via the Network Firewall endpoint's elastic network interface.
This forces traffic from subnet A to subnet B through the firewall.
- D
Create a VPC peering connection between subnet A and subnet B.
Why wrong: Subnets within the same VPC do not need peering.
- E
Create a security group rule that allows traffic between subnet A and subnet B.
Why wrong: Security groups allow or deny traffic but do not route traffic through a firewall.
Quick Answer
The answer is to add a route in subnet A’s route table directing traffic to subnet B via the Network Firewall endpoint’s elastic network interface, and to configure firewall rules that allow the traffic. This is correct because AWS Network Firewall inspects traffic only when route tables explicitly send traffic through the firewall endpoint’s elastic network interface, and the firewall’s stateful or stateless rule groups must permit the desired communication between the subnets. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of how to force traffic inspection without using security groups or VPC peering—a common trap is confusing security group rules with routing logic, or assuming a transit gateway is required. Remember the key: route tables steer the traffic, firewall rules allow it; security groups are for instance-level access, not path control. A useful memory tip is “routes direct, rules permit”—if you see an option about security groups or VPC peering for intra-VPC inspection, it is almost certainly a distractor.
ANS-C01 Network Security, Compliance and Governance Practice Question
This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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 company has a VPC with a CIDR of 10.0.0.0/16. They have two subnets: subnet A (10.0.1.0/24) and subnet B (10.0.2.0/24). They have an AWS Network Firewall deployed in a firewall subnet. They want to inspect all traffic between subnet A and subnet B. Which TWO actions are required? (Choose two.)
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
Configure the Network Firewall rule group to allow the desired traffic between subnets.
Options B and D are correct because Network Firewall requires route tables to direct traffic to the firewall endpoint, and firewall rules must allow the traffic. Option A is wrong because security groups are not used to route traffic. Option C is wrong because VPC peering is not needed. Option E is wrong because the firewall endpoint is in a firewall subnet, not a transit gateway.
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.
- ✗
Attach a transit gateway to the VPC and route traffic through it.
- ✓
Configure the Network Firewall rule group to allow the desired traffic between subnets.
- ✓
Add a route in subnet A's route table that sends traffic to subnet B via the Network Firewall endpoint's elastic network interface.
- ✗
Create a VPC peering connection between subnet A and subnet B.
Why it's wrong here
Subnets within the same VPC do not need peering.
- ✗
Create a security group rule that allows traffic between subnet A and subnet B.
Why it's wrong here
Security groups allow or deny traffic but do not route traffic through a firewall.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group 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 ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Configure the Network Firewall rule group to allow the desired traffic between subnets. — Options B and D are correct because Network Firewall requires route tables to direct traffic to the firewall endpoint, and firewall rules must allow the traffic. Option A is wrong because security groups are not used to route traffic. Option C is wrong because VPC peering is not needed. Option E is wrong because the firewall endpoint is in a firewall subnet, not a transit gateway.
What should I do if I get this ANS-C01 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 ANS-C01 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 20, 2026
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services 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 ANS-C01 exam.
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