VLAN Basic Overview Simply Explained

Exploring Very popular feature most commonly using VLAN Stands for "Virtual Local Area Network," or "Virtual LAN." A VLAN is a custom network created from one or more existing LANs.


In computer networking, a single layer-2 network may be partitioned to create multiple distinct broadcast domains, which are mutually isolated so that packets can only pass between them via one or more routers; such a domain is referred to as a virtual local area network, virtual LAN or VLAN… More sophisticated devices can mark packets through tagging, so that a single interconnect (trunk) may be used to transport data for multiple VLANs…”

Basically a VLAN is a method of created separate networks on the same router for security and segmentation purposes. VLAN setup is a useful procedure if you have some devices on your network that you want to isolate from other devices like multiple guest networks for family friends or office visitors. Provide Internet access with a VLAN without giving them access to your entire network. The settings can easily be changed and adapted to however you want the network to be setup.

Advantages of VLAN

To Avoid Broadcast Problems

When we connect devices into the switch ports, switch creates separate collision domain for each port and single broadcast domain for all ports. Switch forwards a broadcast frame from all possible ports. In a large network having hundreds of computers, it could create performance issue. Of course we could use routers to solve broadcast problem, but that would be costly solution since each broadcast domain requires its own port on router. Switch has a unique solution to broadcast issue known as VLAN. In practical environment we use VLAN to solve broadcast issue instead of router.
Each VLAN has a separate broadcast domain. Logically VLANs are also subnets. Each VLAN requires a unique network number known as VLAN ID. Devices with same VLAN ID are the members of same broadcast domain and receive all broadcasts. These broadcasts are filtered from all ports on a switch that aren’t members of the same VLAN.


To Reduce the size of broadcast domains

VLAN increase the numbers of broadcast domain while reducing their size. For example we have a network of 100 devices. Without any VLAN implementation we have single broadcast domain that contain 100 devices. We create 2 VLANs and assign 50 devices in each VLAN. Now we have two broadcast domains with fifty devices in each. Thus more VLAN means more broadcast domain with less devices.

To add additional layer of security

VLANs enhance the network security. In a typical layer 2 network, all users can see all devices by default. Any user can see network broadcast and responds to it. Users can access any network resources located on that specific network. Users could join a workgroup by just attaching their system in existing switch. This could create real trouble on security platform. Properly configured VLANs gives us total control over each port and users. With VLANs, you can control the users from gaining unwanted access over the resources. We can put the group of users that need high level security into their own VLAN so that users outside from VLAN can’t communicate with them.

Make device management easier

Device management is easier with VLANs. Since VLANs are a logical approach, a device can be located anywhere in the switched network and still belong to the same broadcast domain. We can move a user from one switch to another switch in same network while keeping his original VLAN. For example our company has a five story building and a single layer two network. In this scenario, VLAN allows us to move the users from one floor to another floor while keeping his original VLAN ID. The only limitation we have is that device when moved, must still be connected to the same layer 2 network.

Allow us to implement the logical grouping of devices by function instead of location

VLANs allow us to group the users by their function instead of their geographic locations. Switches maintain the integrity of your VLANs. Users will see only what they are supposed to see regardless what their physical locations are.