AWS Certified Advanced Networking – Specialty (ANS-C00) — Question 291

You need to create a subnet in a VPC that supports 1000 hosts. You need to be as accurate as possible since you run a very large company. What CIDR should you use?

Answer options

• A. /16
• B. /24
• C. /7
• D. /22

Correct answer: D

Explanation

A /22 subnet mask provides 1,024 IP addresses (1,019 usable in an AWS VPC), which is the smallest block that can accommodate 1000 hosts with minimal wastage. A /24 block only provides 256 addresses, which is insufficient, while a /16 block provides 65,536 addresses and is highly inefficient. A /7 block is not supported as a valid VPC subnet size and would be excessively large.