Definition
Subnetting is the process of dividing a larger IP network into smaller, more manageable subnetworks or subnets. This is achieved by borrowing bits from the host portion of an IP address to create a subnet identifier. In practice, subnetting allows for better organization, improved security, and more efficient use of IP addresses within an organization's network. It matters on the job because it helps isolate network segments, control traffic flow, and enhance performance. For instance, a company might subnet its network to separate the guest Wi-Fi from its internal corporate network, preventing unauthorized access. Unlike network segmentation which is a broader concept, subnetting specifically refers to the IP addressing scheme used to achieve this division. Subnetting is a core concept tested on certifications like CompTIA Security+, Network+, and CISSP.