What is VLAN ?

 A VLAN (Virtual Local Area Network) is a logical grouping of devices within a network that allows for the segmentation and isolation of network traffic. It is a method used to create multiple broadcast domains within a single physical network infrastructure.

Traditionally, in a physical network, all devices connected to the same switch or broadcast domain are part of the same LAN (Local Area Network) and can communicate with each other directly. However, VLANs enable network administrators to divide the network into smaller, virtual LANs, even if the devices are physically connected to the same switch.

Here are some key points about VLANs:

Logical Segmentation: VLANs allow for the logical segmentation of a network by grouping devices together based on criteria such as department, function, location, or security requirements. Devices within the same VLAN can communicate with each other as if they were on the same physical LAN, while traffic between VLANs requires routing.

Broadcast Isolation: VLANs provide broadcast isolation, meaning that broadcast traffic sent within a VLAN is limited to devices within that VLAN, reducing unnecessary network traffic and improving network efficiency.

Security and Access Control: VLANs enable enhanced security and access control by separating sensitive or critical devices from the rest of the network. Access control lists (ACLs) and firewall rules can be applied between VLANs to control and restrict communication.

Scalability: VLANs offer scalability by allowing network administrators to create and manage multiple logical networks within a single physical infrastructure. This enables efficient network management and facilitates network expansion without the need for additional physical cabling.

VLAN Tagging: To identify VLAN membership, VLAN tagging is used. Ethernet frames are tagged with a VLAN ID, known as a VLAN tag, which allows switches and routers to distinguish between different VLANs. The most commonly used VLAN tagging protocols are IEEE 802.1Q and ISL (Inter-Switch Link).

Overall, VLANs provide flexibility, scalability, and improved network performance by enabling the logical segmentation of a network into multiple virtual LANs. They are widely used in modern networks to achieve efficient network management, enhance security, and support the diverse requirements of different network environments.