The answer is to use a Gateway Load Balancer with a Gateway Load Balancer endpoint in each subnet. This is the most secure and scalable approach because a Gateway Load Balancer operates at Layer 3, allowing it to transparently intercept and route all traffic—both inbound and outbound—through the firewall appliance without requiring changes to the source or destination IP addresses. On the AWS Certified Security Specialty SCS-C02 exam, this concept tests your understanding of how to enforce east-west and north-south traffic inspection at scale, often appearing in scenarios where a third-party firewall must be inserted into the data path without becoming a bottleneck. A common trap is confusing this with a NAT Gateway, which only handles outbound traffic, or an ALB, which operates at Layer 7 and cannot route raw IP packets for inspection. Remember the mnemonic: “GLB for the full path, NAT for half, ALB for the app.”
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure 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 security engineer needs to ensure that all traffic to an EC2 instance in a VPC is inspected by a network firewall appliance. The firewall is deployed in a separate subnet. What is the MOST secure and scalable way to route traffic through the firewall?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a Gateway Load Balancer with a Gateway Load Balancer endpoint in each subnet.
Option B is correct because a GatewayLoad Balancer with a Gateway Load Balancer endpoint in each subnet allows scaling and transparent inspection. Option A is wrong because a NAT gateway only handles outbound traffic. Option C is wrong because an ALB is for load balancing at layer 7, not for traffic inspection routing. Option D is wrong because a transit gateway is for connecting VPCs, not for routing traffic through a firewall.
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.
✗
Configure a NAT gateway in the firewall subnet and route all traffic through it.
Why it's wrong here
NATgateway only handles outbound traffic from private subnets; inbound traffic is not routed through it.
✓
Use a Gateway Load Balancer with a Gateway Load Balancer endpoint in each subnet.
Use an Application Load Balancer in front of the firewall.
Why it's wrong here
ALB is a layer 7 load balancer and does not support transparent traffic inspection routing.
✗
Create a transit gateway and route traffic through the firewall subnet.
Why it's wrong here
Transit gateway is for inter-VPC routing, not for traffic inspection routing within a VPC.
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 SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Infrastructure Security — This question tests Infrastructure Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Use a Gateway Load Balancer with a Gateway Load Balancer endpoint in each subnet. — Option B is correct because a Gateway Load Balancer with a Gateway Load Balancer endpoint in each subnet allows scaling and transparent inspection. Option A is wrong because a NAT gateway only handles outbound traffic. Option C is wrong because an ALB is for load balancing at layer 7, not for traffic inspection routing. Option D is wrong because a transit gateway is for connecting VPCs, not for routing traffic through a firewall.
What should I do if I get this SCS-C02 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 SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This SCS-C02 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 SCS-C02 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.