ANS-C01 Network Implementation Practice Question
A company is deploying a web application across multiple Availability Zones in a VPC. The application needs to be highly available and scale based on traffic. The architecture includes an Application Load Balancer (ALB) in front of EC2 instances in an Auto Scaling group. The company wants to ensure that if an Availability Zone fails, the ALB can still route traffic to healthy instances in other zones. What should the network engineer implement to meet this requirement?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that cross-zone load balancing is only relevant for Network Load Balancers or that it must be explicitly enabled for ALBs, when in fact ALBs have it enabled by default and it is the key mechanism for multi-AZ failover.
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
✓
Enable cross-zone load balancing on the ALB.
Enabling cross-zone load balancing on an Application Load Balancer (ALB) allows it to distribute incoming traffic evenly across all registered targets in all enabled Availability Zones. If an entire Availability Zone fails, the ALB automatically routes traffic only to healthy instances in the remaining zones, ensuring high availability without requiring manual intervention or additional components.
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 Network Load Balancer instead of an ALB, and enable cross-zone load balancing.
Why it's wrong here
Replacing the ALB with a Network Load Balancer (NLB) and enabling cross-zone load balancing does not address the requirement because the ALB already supports cross-zone load balancing natively; the failure domain is Availability Zone (AZ) failure, and an NLB does not provide the HTTP/HTTPS protocol inspection, path-based routing, or host-based routing that the web application’s ALB architecture requires. This option is tempting because an NLB with cross-zone load balancing distributes traffic across all healthy targets in all enabled AZs, which would be correct for a TCP/UDP-based application that does not need Layer 7 features and where the sole goal is IP-level resilience.
- ✗
Use an ALB with a target group that contains instances from only one Availability Zone, and use Route 53 health checks.
Why it's wrong here
This would not distribute traffic across zones.
- ✗
Deploy one ALB in each Availability Zone and use Route 53 latency-based routing.
Why it's wrong here
This adds complexity and latency-based routing may not failover as quickly as cross-zone load balancing.
- ✓
Enable cross-zone load balancing on the ALB.
Why this is correct
Cross-zone load balancing allows the ALB to distribute traffic across instances in all enabled AZs, providing high availability.
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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.