Virtual Local Area Network

Introduction

VLANs are a logical grouping of different subnets that can be created on a switch. Cisco VLANs allow a network administrator to logically partition a single physical switch into multiple virtual switches. Each VLAN operates as if it was a separate physical network, with its own set of connected devices and separate broadcast domain. In a Cisco VLAN setup, each VLAN is assigned a unique identifier known as a VLAN ID, which is used to differentiate traffic between VLANs. This VLAN ID is added to the Ethernet frame header as a tag, which is used to identify which VLAN the frame belongs to. By dividing a network into VLANs, administrators can provide better security, improve network performance, and simplify network management. For example, VLANs can be used to separate users into different departments or workgroups, or to segment traffic for different types of applications. They can also be used to limit broadcast traffic and prevent unauthorized access to sensitive network resources.