ANS-C01 Network Design Practice Question
A company is designing a high-availability architecture for an application that will be deployed across multiple Availability Zones. Which THREE components are recommended for this design? (Choose three.)
⚠ Common exam trap
AWS often tests the misconception that a single NAT Gateway is sufficient for high availability, but in a multi-AZ architecture, you must deploy a NAT Gateway in each AZ to maintain outbound connectivity during an AZ 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
✓
Application Load Balancer across multiple AZs
An Application Load Balancer (ALB) distributes incoming traffic across multiple targets in different Availability Zones (AZs). By enabling cross-zone load balancing, the ALB can route requests to healthy instances in any AZ, ensuring that if one AZ fails, traffic is automatically redirected to instances in the remaining AZs. This is a foundational component for high availability because it eliminates a single point of failure at the traffic distribution layer.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
One EC2 instance in each AZ
Why it's wrong here
No auto-healing, manual failure handling.
- ✓
Application Load Balancer across multiple AZs
Why this is correct
Distributes traffic across AZs.
- ✓
NAT Gateway in each AZ
Why this is correct
Provides HA for outbound internet access.
- ✓
Auto Scaling group with instances in multiple AZs
Why this is correct
Automatically maintains instance health across AZs.
- ✗
Single NAT Gateway in one AZ
Why it's wrong here
Single point of failure.
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Same concept, more angles
2 more ways this is tested on ANS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is designing a VPC architecture for a web application that must be highly available across multiple Availability Zones. Which TWO components should be deployed in at least two Availability Zones to meet this requirement?
easy- A.Transit Gateway
- B.Internet Gateway
- ✓ C.NAT Gateway
- ✓ D.Application Load Balancer (with subnets in multiple AZs)
- E.VPN connection
Why C: A NAT Gateway is a regional resource that is deployed within a specific Availability Zone, but to achieve high availability across multiple AZs, you must deploy a NAT Gateway in each AZ used by your application. This ensures that if one AZ fails, instances in other AZs can still access the internet or other AWS services through their local NAT Gateway, preventing a single point of failure.
Variation 2. A company is designing a network architecture for a critical application that requires high availability and fault tolerance. The application will be deployed on EC2 instances in an Auto Scaling group across three Availability Zones. The instances must be able to communicate with each other across AZs. Which TWO design decisions improve the fault tolerance of the application? (Choose TWO.)
medium- A.Use a single NAT Gateway in one Availability Zone for internet access
- B.Use VPC endpoints for Amazon S3 to reduce internet dependency
- ✓ C.Configure the Auto Scaling group to launch instances in multiple Availability Zones
- D.Use a single Network Load Balancer in one Availability Zone
- ✓ E.Deploy EC2 instances evenly across three Availability Zones
Why C: Launching instances in multiple Availability Zones (AZs) ensures that if one AZ fails, the Auto Scaling group can still maintain capacity from the remaining AZs, providing fault tolerance. This design leverages the isolation boundaries of AZs within a region, which are physically separate data centers with independent power and networking.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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