Final answer:
The smallest CIDR subnet you can assign for a VPC is /32 for IPv4 and /128 for IPv6, and the largest is typically /16 in practice, though /0 represents all IP addresses.
Step-by-step explanation:
The question regards the size of the CIDR network subnet blocks that can be assigned for a Virtual Private Cloud (VPC). In context of cloud computing and network configuration, CIDR stands for Classless Inter-Domain Routing, which is a method used to allocate IP addresses and route IP packets. The smallest CIDR subnet that can be assigned is /32 for IPv4 and /128 for IPv6. This represents a single IP address. On the other end of the spectrum, the largest subnet block is /0, which effectively represents all IP addresses available, but commonly for a VPC, a /16 subnet (which allows up to 65,536 IP addresses) is a practical upper limit that providers often support. However, the exact maximum size can vary depending on the specific cloud provider's policies and limitations.