When using Amazon VPC, what is the smallest size subnet you can create?

In Amazon VPC (Virtual Private Cloud), the smallest size of a subnet you can create is a /28. A subnet is defined by its CIDR (Classless Inter-Domain Routing) notation, which indicates the number of bits used for the network portion of the address.

A /28 subnet provides a total of 16 IP addresses, of which 14 are usable for hosts (since two addresses are reserved: one for the subnet itself and one for the broadcast address). This makes a /28 subnet a suitable choice for smaller networks or applications that only require a handful of IP addresses, such as connecting a few resources or instances within AWS.

In contrast, larger subnets, such as /16 or /24, would provide more IP addresses than necessary for small implementations. A /30 subnet, while providing only 4 total addresses (with 2 usable), is typically used for point-to-point connections, which wouldn't be categorized as a standard subnet in the same sense as the others. Thus, the choice of a /28 subnet is both practical and in line with AWS VPC capabilities.