ANS-C01 Network Design Practice Question
A company is designing a network for a critical application that requires maximum availability. The application will be deployed across multiple Availability Zones in a single region. Which THREE design choices improve network availability?
⚠ Common exam trap
AWS often tests the misconception that a single NAT gateway is sufficient for high availability because it can route traffic from multiple AZs, but the trap here is that the NAT gateway itself is a zonal resource—if its AZ fails, all outbound traffic is lost, making it a critical single point of failure.
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
✓
Use an Application Load Balancer with targets in multiple Availability Zones
An Application Load Balancer (ALB) with targets in multiple Availability Zones (AZs) improves availability by distributing incoming traffic across healthy targets in different AZs. If one AZ fails, the ALB automatically routes traffic to targets in the remaining AZs, ensuring the application remains accessible. This design eliminates a single point of failure at the load balancer level and leverages the regional nature of the ALB to provide cross-AZ fault tolerance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use an Application Load Balancer with targets in multiple Availability Zones
Why this is correct
Distributes traffic across AZs.
- ✓
Deploy EC2 instances in at least two Availability Zones
Why this is correct
Provides redundancy across AZs.
- ✗
Use a single NAT gateway in one Availability Zone
Why it's wrong here
Single point of failure.
- ✗
Use a single subnet per Availability Zone
Why it's wrong here
Standard practice, not a high availability design choice.
- ✓
Use multiple NAT gateways, one in each Availability Zone
Why this is correct
Avoids single point of failure for outbound traffic.
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Variation 1. A company is designing a network for a critical application that requires high availability across multiple Availability Zones. Which TWO design choices ensure that the application remains available if an entire AZ fails?
medium- A.Deploy resources in a single Availability Zone.
- ✓ B.Deploy resources in at least two Availability Zones.
- C.Use a Network Load Balancer in a single AZ.
- ✓ D.Use an Application Load Balancer that spans multiple AZs.
- E.Use a single EC2 instance with an Elastic IP address.
Why B: Deploying resources in at least two Availability Zones (AZs) is a foundational design pattern for high availability. If an entire AZ fails, the application can continue serving traffic from the remaining AZ(s). This aligns with AWS best practices for fault isolation and is a core requirement for achieving an SLA-backed multi-AZ architecture.
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.