What is VLAN (Virtual LAN)?
A VLAN, or Virtual LAN, splits one physical network into several isolated logical networks. Devices on VLAN 10 cannot see devices on VLAN 20 even though they share the same switches and cables โ the separation is enforced by tagging each data frame with its VLAN number. One cable can carry many VLANs, and the router controls what, if anything, may cross between them.
Practical Indian examples: a hotel keeps guest Wi-Fi on one VLAN and its billing computers and CCTV on others, so a guest's infected laptop cannot touch the front-office PC; an ISP delivers each colony or building on its own VLAN over a single fibre backbone, simplifying troubleshooting and stopping one customer's broadcast storm from flooding everyone. VLANs cost nothing โ managed switches from โน2,500 support them.