The primary purpose of subnetting in a network is to enhance both performance and security by dividing a larger network into smaller, more manageable segments known as subnets.

Subnetting is a technique employed in IP networking that involves partitioning a large network into smaller subnets by modifying the subnet mask of an IP address. This process not only improves network performance but also bolsters security.

When a network is segmented into subnets, it helps to alleviate network congestion. This reduction in congestion occurs because traffic is restricted to its specific subnet, preventing it from impacting other segments of the network. For instance, if a device within one subnet broadcasts a message, that message will only reach other devices within the same subnet, rather than being disseminated throughout the entire network. This targeted traffic management can lead to a significant decrease in overall network traffic and an improvement in performance.

Moreover, subnetting enhances network security. By segregating the network into various subnets, the flow of traffic between them can be controlled more effectively. This means that if a security breach occurs in one subnet, it can be isolated within that subnet, thereby preventing it from spreading to the rest of the network. This capability is particularly advantageous for large organizations, where different departments may have distinct security needs.

Additionally, subnetting contributes to more efficient management of IP addresses. In a large network without subnets, tracking and administrating IP addresses can become cumbersome. However, by dividing the network into subnets, a specific range of IP addresses can be allocated to each subnet, simplifying the tracking and management process.

Finally, subnetting can facilitate geographical separation within a network. For example, a multinational corporation can establish separate subnets for its offices located in different countries. This division can enhance the management of network resources and improve communication speeds, as data transmission does not need to traverse unnecessary routes.