• Broadcast Control: Broadcasts are required for the normal function of a network. Many protocols and applications depend on broadcast communication to function properly. A layer 2 switched network is in a single broadcast domain and the broadcasts can reach the network segments which are so far where a particular broadcast has no scope and consume available network bandwidth. A layer 3 device (typically a router) is used to segment a broadcast domain.
If we segment a large LAN to smaller VLANs we can reduce broadcast traffic as each broadcast will be sent on to the relevant VLAN only.
• Security: VLANs provide enhanced network security. In a VLAN network environment, with multiple broadcast domains, network administrators have control over each port and user. A malicious user can no longer just plug their workstation into any switch port and sniff the network traffic using a packet sniffer. The network administrator controls each port and whatever resources it is allowed to use.
VLANs help to restrict sensitive traffic originating from an enterprise department within itself.
• Cost: Segmenting a large VLAN to smaller VLANs is cheaper than creating a routed network with routers because normally routers costlier than switches.
• Physical Layer Transparency: VLANs are transparent on the physical topology and medium over which the network is connected.