AWS Certified SysOps Administrator SOA-C01 – Question294

A user has created a VPC with public and private subnets using the VPC Wizard. The VPC has CIDR 20.0.0.0/16. The private subnet uses CIDR 20.0.0.0/24. Which of the below mentioned entries are required in the main route table to allow the instances in VPC to communicate with each other?

A. Destination : 20.0.0.0/24 and Target : VPC
B. Destination : 20.0.0.0/16 and Target : ALL
C. Destination : 20.0.0.0/0 and Target : ALL
D. Destination : 20.0.0.0/24 and Target : Local

Correct Answer: D

Explanation:

Option A doesn’t use standard AWS terminology (you don’t route to “VPC”), and because the mask is /24, it would only allow the instances in the private subnet to communicate with each other, not all the instances in the VPC as the question asked. Here’s an example VPC route table for a public subnet (i.e. it routes to the IGW). Option D is the correct one.