The correct choice is to create a Gateway Load Balancer and configure the appliance as a target. This works because a Gateway Load Balancer operates at Layer 3, allowing it to transparently intercept and redirect traffic between instances within the same subnet by using the Gateway Load Balancer endpoint as the next hop in the route table, thereby enabling intra-subnet traffic inspection without altering source or destination IP addresses. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of how GWLB differs from traditional load balancers—it is not for distributing traffic to clients but for inserting network appliances inline. A common trap is confusing GWLB with Transit Gateway or VPC Peering, which handle inter-subnet or inter-VPC traffic, not same-subnet inspection. Memory tip: think of GWLB as a “bouncer” that stands inside the same room (subnet) to check every conversation between guests (instances) without moving them to another room.
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 is deploying an application across multiple Availability Zones in a single AWS Region. The application requires that all traffic between EC2 instances in the same subnet be inspected by a network appliance. Which configuration should be used to meet this requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a Gateway Load Balancer and configure the appliance as a target
Option B is correct because a GatewayLoad Balancer (GWLB) can be deployed in a subnet and configured to route traffic between instances in the same subnet through the network appliance. Option A is incorrect because a Transit Gateway is used for inter-VPC routing, not intra-subnet inspection. Option C is incorrect because a VPC peering connection connects different VPCs. Option D is incorrect because AWS Network Firewall inspects traffic at VPC boundaries, not within a subnet.
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.
✗
Set up a VPC peering connection between the subnets
Why it's wrong here
VPC peering connects different VPCs, not subnets within the same VPC.
✗
Use a Transit Gateway to route traffic through the appliance
Why it's wrong here
Transit Gateway is used for inter-VPC connectivity, not intra-subnet traffic inspection.
✗
Deploy AWS Network Firewall in the subnet
Why it's wrong here
AWS Network Firewall inspects traffic crossing VPC boundaries, not within a subnet.
✓
Create a Gateway Load Balancer and configure the appliance as a target
Why this is correct
GWLB can be used to inspect all traffic between instances in the same subnet via a GatewayLoad Balancer Endpoint.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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.
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Create a Gateway Load Balancer and configure the appliance as a target — Option B is correct because a Gateway Load Balancer (GWLB) can be deployed in a subnet and configured to route traffic between instances in the same subnet through the network appliance. Option A is incorrect because a Transit Gateway is used for inter-VPC routing, not intra-subnet inspection. Option C is incorrect because a VPC peering connection connects different VPCs. Option D is incorrect because AWS Network Firewall inspects traffic at VPC boundaries, not within a subnet.
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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Question Discussion
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