The correct choice is to configure a Gateway Load Balancer and Gateway Load Balancer endpoints in the VPC. This solution enables inline traffic inspection by placing a third-party security appliance transparently in the data path, allowing all traffic to and from your EC2 instances to be inspected without changing their private IP addresses. The Gateway Load Balancer acts as a virtual overlay that forwards traffic to the appliance fleet, while the Gateway Load Balancer endpoints serve as entry and exit points in each subnet, ensuring packets are routed through the inspection chain. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of how to insert network functions without disrupting existing IP assignments—a common trap is choosing a Network Load Balancer, which only distributes traffic and cannot perform inline inspection. Remember the key distinction: Gateway Load Balancer is for transparent traffic inspection, not just load balancing. A helpful memory tip is “GWLBe for inline, NLB for divide”—Gateway Load Balancer endpoints keep IPs intact while inspecting traffic inline.
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 wants to ensure that all traffic to and from its Amazon EC2 instances in a VPC is inspected by a third-party security appliance. The instances are in private subnets and must maintain their private IP addresses. Which solution 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
✓
Configure a Gateway Load Balancer and Gateway Load Balancer endpoints in the VPC
Option A is correct because GatewayLoad Balancer with a Gateway Load Balancer endpoint (GWLBe) allows you to insert third-party appliances inline for traffic inspection without changing the instances' IP addresses. Option B is wrong because a Network Load Balancer is for load balancing, not inline inspection. Option C is wrong because VPC Peering does not provide traffic inspection. Option D is wrong because a Transit Gateway with a VPN does not provide inline inspection.
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.
✗
Deploy a Transit Gateway with a site-to-site VPN to the appliance
Why it's wrong here
Transit Gateway with VPN does not provide inline inspection within the VPC.
✓
Configure a Gateway Load Balancer and Gateway Load Balancer endpoints in the VPC
Why this is correct
GatewayLoad Balancer with GWLBe allows transparent inline inspection of traffic.
Use VPC Peering to connect to a central inspection VPC
Why it's wrong here
VPC Peering connects VPCs but does not inherently inspect traffic unless a device is configured.
✗
Set up a Network Load Balancer in front of the instances
Why it's wrong here
NLB distributes traffic but does not inspect it; it preserves source IP but does not insert a security appliance.
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.
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 a Gateway Load Balancer and Gateway Load Balancer endpoints in the VPC — Option A is correct because Gateway Load Balancer with a Gateway Load Balancer endpoint (GWLBe) allows you to insert third-party appliances inline for traffic inspection without changing the instances' IP addresses. Option B is wrong because a Network Load Balancer is for load balancing, not inline inspection. Option C is wrong because VPC Peering does not provide traffic inspection. Option D is wrong because a Transit Gateway with a VPN does not provide inline inspection.
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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