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Introduction to VLAN

VLAN refers to Virtual Local Area Network is a virtual LAN that extends its functionalities beyond a single LAN.  Through VLAN a network is divided into different logical segments known as broadcast domains. The computers in the VLAN acts as they are connected with the same LAN segment even they are located on the different network segments. In the VLAN, computers can move from one location to another and they can still be the part of the same VLAN.  . VLAN offers many advantages over the traditional local area network.


The main advantages of the VLAN includes high performance, simplified network administration, security, low cost and the creation of the virtual groups to avoid the collision and data loss in the network. VLAN controls the bandwidth allocations and provides the flexibility and ease of work to the users.  In the VLAN, the computers do not need to be physically located at the same place. Though it is a logical entity it is created and configured through the software.


Types of VLAN

There are two main types of the VLANs.

Frame Based VLANs:  This kind of VLAN is used in the Ethernet networks and it uses the frame tagging technique. The two main types of the frame tagging are ISL (Inter Switch Link) and IEEE 802.10. With the 802.10 standards it is possible to deploy the VLAN not only in the Ethernet but also in the Token rink and FDDI.

Cell Based VLANs: This type of the VLAN is used in the ATM networks with LAN emulation also known as LANE.  LANE allows the computers in the LAN segment to communicate by using the ATM networks without requiring special hardware or software configurations.


VLAN Classifications

VLAN can be classified into the following types.

  • Layer1 VLAN:  It is based on the ports that belongs the VLAN.
  • Layer2VLAN: It is based on the MAC address of the computer. Layer2 VLAN is also based on the protocol type.
  • Layer3VLAN: It is based on the layer3 header.  The IP address and the subnet mask are used to determine and classify the VLAN membership.
  • High Layer VLAN:  The membership of the VLAN is determined by using the service of applications or the combination of both.

Why VLAN is required?

VLAN is required due to the following reasons.

  • If you have a lot of broadcast traffic in your network.
  • You have more than 200 network devices in your network and you want to avoid collisions and data lost.
  • You want to make the users on the same broadcast domain because the users are using the same network application.
  • You need to make single switch.
  • You want to allow the more security to a group of users.

Virtual networking provides unmatched flexibility.  Today there are many VLAN solutions available to LAN. Cisco Systems offer comprehensive VLAN solution that allows the remote and geographically dispersed users to come together and become a part of the same network by forming VLAN workgroup topologies. 

Cisco offers the virtualization solutions to all types of networks including Ethernet, FDDI, Token ring and ATM.
The network devices in the VLAN are connected by following three ways.

  • Trunk Link
  • Access Link
  • Hybrid Link

Although VLAN offers many advantages it has following limitations.

  • Device Limitations
  • Port Limitations
  • Broadcast Limitations


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