Which CIDR block size is the smallest commonly used for a VPC in this context?

Which CIDR block size is the smallest commonly used for a VPC in this context?

• A. /24
• B. /16
• C. /32
• D. /28

Answer: (A)

A VPC’s CIDR block size determines how many IP addresses are available for the network and its subnets. In AWS, a VPC can be defined with a CIDR from /16 down to /28. The smallest possible, /28, provides only 16 addresses, which is usually far too little once you start creating multiple subnets across availability zones and adding resources. A /24 block, on the other hand, gives 256 addresses, which is enough to carve out several subnets (typically one per AZ) and still leave room for growth and AWS infrastructure needs. Because of that practical balance between having enough addresses and not wasting space, /24 is the smallest CIDR size commonly used for a VPC. Larger blocks like /16 offer ample room but can be wasteful for smaller deployments, while /32 would give just a single IP, which isn’t feasible for a VPC.

A VPC’s CIDR block size determines how many IP addresses are available for the network and its subnets. In AWS, a VPC can be defined with a CIDR from /16 down to /28. The smallest possible, /28, provides only 16 addresses, which is usually far too little once you start creating multiple subnets across availability zones and adding resources. A /24 block, on the other hand, gives 256 addresses, which is enough to carve out several subnets (typically one per AZ) and still leave room for growth and AWS infrastructure needs. Because of that practical balance between having enough addresses and not wasting space, /24 is the smallest CIDR size commonly used for a VPC. Larger blocks like /16 offer ample room but can be wasteful for smaller deployments, while /32 would give just a single IP, which isn’t feasible for a VPC.