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Computer Science 220: Fundamentals of Routing and Switching11 chapters | 58 lessons
A Virtual Local Area Network (VLAN) refers to a logical grouping of different hosts in a similar broadcast domain. VLANs simplifies the task for the IT network administrators to divide & make groups in a network, based on their functional and security requirements without having to plug/unplug physical LAN cables or modify the existing IT network infrastructure.
A switch is a physical networking device that connects multiple hosts on a Local Area Network (LAN) like our computers, laptops, tablets and more. The switch helps to route the data back and forth in-between hosts. A switch has many ports based on its models and manufacturers, and each port serves one host device on a LAN.
An interface is the logical connection and configuration on a switch port that helps in communication. For example, when a host system operated using one switch port through an Ethernet cable, this communication channel can be called as an interface.
VLANs get configured on a switch by placing few interfaces (like tagging) into a single broadcast domain. A single VLAN can spread across various switches but remain in the same subnet or the broadcast domain. VLANs are similar to physical LANs; the difference is that it allows grouping of the host devices, even if they on different switches.
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A broadcast domain in a switch refers to the domain that receives the broadcast messages. Broadcasting a message means to send it to all the connected host devices that are a part of that domain. By default, all the ports are grouped in a common broadcast domain in a switch or a hub. Hence, the switch floods (sends) the message received from one port to all the other connected ports; so all the hosts that are attached to these ports receive the same message. This process is called flooding.
Imagine that a switch has eight ports and eight different hosts are connected to these ports, if a broadcast message reaches the switch from one of these hosts- the switch forwards them to all other seven hosts as they are a part of the common broadcast domain, which comes configured from the factory.
In contrast, the ports on a router are not in a common broadcast domain; it treats each port separately.
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In the above diagram, there are two switches and two broadcast domains. Switch 1 has three hosts connected to it, and all the three hosts share the same broadcast domain. Similarly, all the three host systems of switch 2 belong to a common broadcast domain.
Let us understand VLAN and its implementation with a real-world example.
Branch A is dedicated to the Production department, so it has 2 systems for Production, 1 system for Research, 1 for HR, and 1 for Admin.
And similarly,
Branch B is dedicated to the Research department, so it has 2 systems for Research work and 1 system for Production, 1 for HR and 1 for Admin.
Below is the data representation in tabular format for each branch and number of systems in them.
Branch Name | Production Systems | Research Systems | Admin Systems | HR Systems |
---|---|---|---|---|
Branch A | 2 | 1 | 1 | 1 |
Branch B | 1 | 2 | 1 | 1 |
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With the default configuration, all the ports on a switch are in the same broadcast domain. Thus, the users in the Production and Research departments of each branch can access the data stored in HR and Admin systems, as they are a part of same broadcast domains.
Using VLAN, it is possible to set logical boundaries in this LAN. Four VLANs can be created for the above scenario and can be assigned to related systems as follows:
There is no change in the physical configurations, but we have logically grouped the systems based on their functionalities and roles. The VLANs now need a router for inter VLAN communication as each VLAN a separate LAN in itself. A router comes with advanced security features.
Using VLAN, we have virtually separated one single big local area network (LAN) into four smaller systems. These four VLANs never share the broadcast message as each VLAN is under different broadcast domains. VLAN thus enhances the security of the network. Now, users in the Production and Research departments won't be able to access the data in HR and Admin departments directly.
The table shows the total number of systems for both the branches, as they are now a part of one VLAN.
Production Systems-VLAN1 | HR Systems-VLAN2 | Admin Systems-VLAN3 | Research Systems- VLAN4 |
---|---|---|---|
3 | 2 | 2 | 3 |
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A Virtual Local Area Network (VLAN) is a logical division of computer systems in a LAN (Local Area Network) that are connected to a switch, based on their functionalities. VLANs are implemented for enhancing security between various departments and also for easy configuration. By default, the host systems on a switch are in the same broadcast domain, but VLAN separates them into various broadcast domains.
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Computer Science 220: Fundamentals of Routing and Switching11 chapters | 58 lessons