VLANs (Virtual Local Area Networks)

VLANs, or Virtual Local Area Networks, are a fundamental networking concept used to logically segment a single physical network into multiple broadcast domains. Here are the key aspects of VLANs:

1. Purpose: VLANs allow network administrators to segment a larger network into smaller, isolated broadcast domains. This segmentation can improve network performance, security, and manageability.

2. Logical Grouping: VLANs are created by assigning specific ports on switches or other network devices to a VLAN ID. Devices within the same VLAN can communicate with each other as if they were on the same physical network, regardless of their physical location.

3. Broadcast Control: By dividing the network into VLANs, broadcast traffic is contained within each VLAN, reducing unnecessary traffic propagation across the entire network and improving overall network efficiency.

4. Security: VLANs provide a level of security by isolating traffic within a VLAN. Devices in one VLAN typically cannot communicate directly with devices in another VLAN without routing through a Layer 3 device, such as a router or a Layer 3 switch.

5. Flexibility: VLANs are flexible and can be configured based on different criteria such as departments, functions, or security requirements. This allows for better organization and management of network resources.

6. Types of VLANs:

   • Port-Based VLANs: Ports on switches are assigned to specific VLANs based on the physical port.
   • Tagged VLANs (802.1Q): Allows multiple VLANs to traverse a single link or trunk, with each frame tagged to indicate which VLAN it belongs to.
   • Native VLAN: In 802.1Q tagging, frames from the native VLAN are not tagged when sent over a trunk link.
   • Voice VLANs: Specifically designed to prioritize voice traffic (e.g., VoIP) by separating it from other data traffic.

7. Inter-VLAN Communication: When devices in different VLANs need to communicate, a router or Layer 3 switch is required to route traffic between VLANs. This process can be managed using static routing or dynamic routing protocols.

Overall, VLANs provide a powerful way to segment and manage networks, improving performance, security, and flexibility in modern network infrastructures.