When a classful network is split into several smaller networks, the smaller networks are called?

When a classful network is divided into several smaller networks, these smaller networks are referred to as subnets. Subnetting is a process used to improve network management and efficiency by allowing the division of a larger network into more manageable segments. Each subnet operates as a separate network, which can enhance performance and security, and allows for more efficient utilization of IP addresses. By breaking a larger network into subnets, organizations can control traffic flow, reduce congestion, and better manage resource allocation, which is especially important given the limitations of available IP addresses.

The other terms listed do not accurately describe this specific action of dividing a classful network into smaller networks. Segmentation typically refers to breaking down network traffic into smaller pieces for better handling, rather than the structural division of IP address space. Classful networks denote the original method of IP address classification without subnetting, and network zones usually refer to logical groupings within a network that may not necessarily be related to IP addressing. Thus, the correct terminology in this context is subnets.