ANS-C01 Network Design Practice Question
A company is designing a VPC with multiple subnets across three Availability Zones. The application requires that all traffic between subnets within the same AZ stay within that AZ to minimize latency and data transfer costs. Which configuration achieves this?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that a single route table or a centralized service like Transit Gateway can achieve AZ-level traffic isolation, but the key is that local VPC routing inherently stays within the AZ only when the route table is per-AZ and contains only the local VPC CIDR, not when a shared route table or additional network appliances are introduced.
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
✓
Create a route table for each AZ and associate the subnets in that AZ with the route table. Ensure the route tables have only local routes for the VPC CIDR.
Each Availability Zone (AZ) has its own route table with only the local VPC CIDR route. This ensures that traffic between subnets in the same AZ uses the VPC's local routing, which stays within the AZ's physical infrastructure, minimizing latency and avoiding cross-AZ data transfer costs. AWS VPC local routes inherently keep traffic within the same AZ when source and destination are in the same AZ, as the underlying network fabric directs traffic locally without traversing AZ boundaries.
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 a single route table for all subnets and add specific routes for each AZ.
Why it's wrong here
Does not guarantee intra-AZ routing.
- ✗
Use an AWS Transit Gateway with separate attachments for each AZ.
Why it's wrong here
Transit gateway routes traffic centrally, not necessarily within the same AZ.
- ✗
Create a VPC peering connection between subnets in the same AZ.
Why it's wrong here
Unnecessary and doesn't control routing.
- ✓
Create a route table for each AZ and associate the subnets in that AZ with the route table. Ensure the route tables have only local routes for the VPC CIDR.
Why this is correct
Local routing within the same AZ is used.
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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.