Introduce basic network
LAN
Lan is a local area network that is defined and covered by a network address and broadcast address is the same. You need to remember also that the router device will stop whatever it protocolnya broadcast traffic, but the switch will automatically be forwarded.
VLAN
VLAN is a Virtual LAN is a LAN network that virtually created on a switch. In standard switch usually forwards traffic from one port to all other ports when there is traffic with the same broadcast domain through the port. For the special switches, they are able to make several different LANs with different id in every port, and will only forward traffic to ports that have the same id. Special type switch is actually automatically install VLAN in it (vlan id = 1) which consists of all the existing ports.
Why VLANs are needed ?
