At which layer of the OSI model do VLANs operate?

VLANs, or Virtual Local Area Networks, operate at Layer 2 of the OSI model, which is the Data Link layer. This layer is responsible for node-to-node data transfer and handles addressing through MAC (Media Access Control) addresses.

VLANs segment a physical network into multiple logical networks at Layer 2. This segmentation improves network efficiency by reducing broadcast domains, allowing devices within the same VLAN to communicate directly while isolating traffic from devices in other VLANs.

By functioning at Layer 2, VLANs also utilize features like tagging, often implemented via protocols such as IEEE 802.1Q, to identify which VLAN a frame belongs to as it traverses a switch. This capability is crucial for managing network resources and enhancing security in multi-tenant environments.

Layers 1, 3, and 4 relate to different functionalities: Layer 1 is concerned with the physical aspects of networking, Layer 3 manages logical addressing and routing between different networks, and Layer 4 deals with transport protocols such as TCP and UDP, which are responsible for end-to-end communication. Therefore, the correct operation of VLANs at the Data Link layer is fundamental to their purpose and functionality in modern network design.