Which of the following are valid VPC CIDRs to add to an existing VPC? Choose 2 answers from the options given below

Answer options:

A.10.0.0.0/24
B.10.0.0.0/29
C.20.0.0.0/10
D.20.0.0.0/27

Answer – A and D
The AWS documentation mentions the following
When you create a VPC, you must specify an IPv4 CIDR block for the VPC. The allowed block size is between a /16 netmask (65,536 IP addresses) and /28 netmask (16 IP addresses)
For more information on VPC Sizing, please refer to the below link:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Subnets.html#VPC_Sizing