ANS-C01 Network Implementation Practice Question
A company is using AWS CloudFormation to deploy a VPC with two public subnets and two private subnets across two Availability Zones. The template includes an internet gateway and a NAT gateway in each public subnet. The company needs to ensure that instances in the private subnets can access the internet. Which route table configuration should be used?
⚠ Common exam trap
Watch out — candidates often assume a single NAT gateway is sufficient for cost savings, overlooking the high-availability requirement and cross-AZ data transfer costs that AWS explicitly tests in multi-AZ VPC designs.
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
✓
Add a route 0.0.0.0/0 pointing to the NAT gateway in the same AZ in each private subnet route table.
Private subnets require a default route (0.0.0.0/0) pointing to a NAT gateway in the same Availability Zone to ensure internet-bound traffic is source-NATed. This design maintains high availability by avoiding cross-AZ data transfer costs and single points of failure. The NAT gateway must be placed in a public subnet, and the private subnet route table must explicitly direct traffic to it.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add a route to the internet gateway in the private subnet route tables.
Why it's wrong here
Private subnets cannot have direct IGW routes.
- ✗
Add a route to the NAT gateway in the public subnet route tables.
Why it's wrong here
Public subnets do not need NAT routes.
- ✓
Add a route 0.0.0.0/0 pointing to the NAT gateway in the same AZ in each private subnet route table.
Why this is correct
Provides high availability and AZ independence.
- ✗
Add a route 0.0.0.0/0 pointing to a single NAT gateway in both private subnet route tables.
Why it's wrong here
Single point of failure; best practice is one NAT per AZ.
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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.