Its the first major topic of our Cisco switch world. Well to start of let me tell you one secret, if you are using a managed switch, you are using VLANs, so its not that alien of a topic. Yes its true even if you have not came across setting up VLANs while configuring your networks (using managed switches), you are using VLAN, as its default “VLAN 1” every port of a managed switch belongs to VLAN 1 by default. So what is VLAN, lets start with a brief discussion of what switches do; Well they are the Layer 2 (OSI) device and divide collision domain on per port basis i.e. each port of a switch is a separate collision domain. But by default it does not divide the broadcast domain. To have separate broadcast domains we need a layer 3 device like a router. But there is a mechanism to divide broadcast domain at layer 2, and that mechanism is referred as VLANs. VLANs logically group users by segmenting broadcast domain. As per Cisco, VLANs = Broadcast Domain = Subnet End nodes on a giv...
Cisco Switch and Router Configuration