What is the primary purpose of an IP subnet?

The primary purpose of an IP subnet is to improve routing efficiency and enhance security within a network. By dividing a larger network into smaller, more manageable sub-networks (subnets), data can be routed more effectively. This segmentation helps in reducing traffic congestion, as local traffic is kept within the subnet rather than passing through the entire network, which can lead to increased performance.

Additionally, subnets can enhance security because they allow network administrators to implement policies and controls that limit access and monitor traffic within different segments of the network. For instance, sensitive data can be isolated in a specific subnet, making it more difficult for unauthorized users to access it from other parts of the network. This also allows for easier management of network permissions and policies.

The other options reflect purposes that are less accurate concerning the fundamental role of subnets in networking. For instance, connecting multiple networks directly pertains more to network routers than subnets themselves. While increasing internet speed might be a side effect of improved routing, it's not the primary purpose of subnetting. Backup for network devices does not relate to subnets, as that involves data redundancy and resilience strategies rather than network segmentation.