ANS-C01 Network Design Practice Question
A company has a VPC with multiple subnets across two Availability Zones. They are designing a highly available web application using an Application Load Balancer (ALB) and EC2 instances in an Auto Scaling group. Which of the following is the most resilient and cost-effective design for the network layer?
⚠ Common exam trap
Many exam-takers assume deploying a load balancer in each AZ (Option D) is necessary for high availability, but they overlook that a single ALB with subnets in multiple AZs and cross-zone load balancing already provides full AZ-level redundancy at lower cost and complexity.
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
✓
Deploy a single ALB with subnets in two AZs and enable cross-zone load balancing.
Deploying a single Application Load Balancer (ALB) with subnets in two Availability Zones (AZs) and enabling cross-zone load balancing provides high availability and fault tolerance at the network layer. The ALB automatically distributes incoming traffic across healthy targets in all enabled AZs, eliminating the need for multiple load balancers and reducing costs while maintaining resilience. This design leverages the ALB's native ability to handle AZ failures by routing traffic only to healthy AZs, making it both resilient and cost-effective.
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 Network Load Balancer (NLB) in each AZ and associate them with a single ALB.
Why it's wrong here
This adds complexity and cost; an ALB alone is sufficient.
- ✗
Deploy an ALB in one AZ and EC2 instances in the same AZ.
Why it's wrong here
This is not highly available if the AZ fails.
- ✓
Deploy a single ALB with subnets in two AZs and enable cross-zone load balancing.
Why this is correct
Cross-zone balancing ensures traffic is distributed across instances in all AZs.
- ✗
Deploy an ALB in each AZ and use Route 53 weighted routing.
Why it's wrong here
An ALB is regional; deploying per AZ is unnecessary and costly.
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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.