One of the technologies that improve network performance is the separation of large broadcast domains into smaller ones. By design, routers block broadcast traffic. But, routers usually have a limited number of LAN interfaces. A router’s main role is to move data between different networks. The router does not provide network access to end devices. The access layer switches are responsible for connectivity to end devices. The VLAN on Layer 2 switches reduce the size of broadcast domains. VLANs are incorporated into network design making it easier for a network to support the goals of an organization. Mostly VLAN is used within switched LANs.
The VLAN create a logical broadcast domain that consists of different physical LAN segments. it improves network performance by separating large broadcast domains into smaller broadcast domains. If a device in one VLAN sends a broadcast data, all devices in that VLAN receive the data, but devices in other VLANs do not.
What is VLANs
Virtual Local Area Network provides segmentation within a switched network. It is a technique that group devices within a LAN. A group of devices within a VLAN communicate like they are connected to the same wire. VLANs are based on logical connections, in place of physical connections. it permits a network administrator to divide larger networks based on factors like function, project team, or application, without hold for the physical location of the user or device.
Devices inside a VLAN work like they are in their own independent network; though they share a common infrastructure with other VLANs. Any switch port can belong to any VLAN, and unicast; broadcast and multicast packets are forwarded and flooded only to end station within the VLANs. Every VLAN is work like a separate logical network; and data destined for stations, not in the VLAN must be forwarded through a router or device that supports routing. VLANs make possible the implementation of access and security policies to particular groupings of users. Each switch port can be assigned to only one VLAN except some cases. The figure below illustrates the layout of VLANs.