ANS-C01 Gateway Load Balancer (GWLB) Practice Question
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?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that intra-subnet traffic can be intercepted by a firewall or routing construct, but in AWS, traffic between instances in the same subnet is Layer 2 and never hits a route table, so only a Gateway Load Balancer (or an inline appliance with proxy ARP) can inspect it.
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
✓
Create a Gateway Load Balancer and configure the appliance as a target
A Gateway Load Balancer (GWLB) can inspect intra-subnet traffic between EC2 instances in the same subnet. Traffic between instances in the same subnet is Layer 2 and does not traverse route tables, so traditional routing methods cannot intercept it. GWLB uses Geneve encapsulation to transparently redirect traffic at the hypervisor level to the appliance targets without modifying the route table. The appliance must be configured to handle this encapsulation. Other options do not support inspection of same-subnet traffic.
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 Gateway Load Balancer Endpoint.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.