By Ashar Anwar

Objectives

After watching this recorded lecture you will be able to define:

• VLANs• Basic operation of VLANs• Benefits of VLANs• Common VLANs Terminologies.

Introducing VLANs

• Consider a small community college with student dorms and the faculty offices all in one building.

• A year later, the college has grown and now has 3 buildings.

• How can the network accommodate the shared needs of the geographically separated departments?

VLAN Overview

• The solution for the community college is to use a networking technology called a virtual LAN (VLAN).

In the figure, one VLAN is created for students and another for faculty.

VLAN Overview • For computers to communicate

on the same VLAN,

Each must have an IP address and a subnet mask that is consistent for that VLAN. The switch has to be configured with the VLANEach port in the VLAN must be assigned to the VLAN. A switch port with a singular VLAN configured on it is called an access port. Remember, just because two computers are physically connected to the same switch does not mean that they can communicate. Devices on two separate networks and subnets must communicate via a router (Layer 3), whether or not VLANs are used.

VLAN OperationsVLAN Operations

• Each logical VLAN is like a separate physical bridge

Switch A

GreenVLAN

BlackVLAN

RedVLAN

Switch A

GreenVLAN

BlackVLAN

RedVLAN

Switch B

GreenVLAN

BlackVLAN

RedVLAN

• VLANs can span across multiple switches

• Management/HR Department (red)• Accounting Department (black) • Data Recovery & IT Department (green)

Benefits of a VLAN• The primary benefits of using VLANs are:

–Security

–Cost reduction

–Higher performance

–Broadcast storm mitigation

–Improved IT staff efficiency

–Simpler project or application management

Common VLAN Terminologies• Data VLAN

• Default VLAN

Common VLAN Terminologies• Native VLAN

• Management VLAN