Definition
A VLAN (Virtual Local Area Network) is a logical grouping of network devices that behave as if they are on the same physical network segment, regardless of their actual physical location. It achieves this by segmenting a larger physical network into smaller, broadcast domains, allowing administrators to isolate traffic and improve network performance. VLANs are configured on network switches, enabling granular control over network access and traffic flow. For example, a company might use separate VLANs for its finance department, its marketing department, and its guest Wi-Fi to enhance security and prevent unauthorized access. While similar in function to subnetting, VLANs operate at Layer 2 (data link layer) of the OSI model, whereas subnetting operates at Layer 3 (network layer). Understanding VLANs is crucial for network security and administration roles and is a common topic on certifications like CompTIA Security+ and CISSP.