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[Sticky] What is VLAN? Types, Advantages and disadvantages

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What is VLAN

The full form of VLAN is defined as Virtual Local Area Network. Vlan is a custom network which is created from one or more local area networks. It enables a group of devices available in multiple networks to be combined into one logical network. The result becomes a virtual LAN that is administered like a physical LAN. 

How VLAN works

Here is how VLAN works:

  • VLANs in networking are identified by a number.
  • A Valid range is 1-4094. On a VLAN switch, you assign ports with the proper VLAN number.
  • The switch then allows data which needs to be sent between various ports are in the same VLAN.
  • Since almost all networks are larger than a single switch, there should be a way to send traffic between two switches.
  • One simple and easy way to do this is to assign a port on each network switch with a VLAN and run a cable between them.

VLAN Ranges

Here are the important ranges of VLAN:

Range Description
VLAN 0-4095 Reserved VLAN, which cannot be seen or used.
VLAN 1: This is a default VLAN of switches. You cannot delete or edit this VLAN, but it can be used.
VLAN 2-1001: It is a normal VLAN range. You can create, edit, and delete it.
VLAN 1002-1005: These ranges are CISCO defaults for token rings and FDDI. You cannot delete this VLAN.
VLAN 1006-4094:

It is an extended range of VLANs.


Characteristics of VLAN

Here are the important characteristics of VLAN:

  • Virtual LANs offer structures for making groups of devices, even if their networks are different.
  • It increases the broadcast domains possible in a LAN.
  • Implementing VLANs reduces the security risks as the number of hosts which are connected to the broadcast domain decreases.
  • This is performed by configuring a separate virtual LAN for only the hosts having sensitive information.
  • It has a flexible networking model that groups users depending on their departments instead of network location.
  • Changing hosts/users on a VLAN is relatively easy. It just needs a new port-level configuration.
  • It can reduce congestion by sharing traffic as individual VLAN works as a separate LAN.
  • A workstation can be used with full bandwidth at each port.
  • Terminal reallocations become easy.
  • A VLAN can span multiple switches.
  • The link of the trunk can carry traffic for multiple LANs.

Types of VLANs

1- Port-Based VLAN

Port-based VLANs groups virtual local area network by port. In this type of virtual LAN, a switch port can be configured manually to a member of VLAN.

Devices that are connected to this port will belong to the same broadcast domain, that is because all other ports are configured with a similar VLAN number.

The challenge of this type of network is to know which ports are appropriate for each VLAN. The VLAN membership can’t be known just by looking at the physical port of a switch. You can determine it by checking the configuration information.

2- Protocol Based VLAN

This type of VLAN processes traffic based on a protocol that can be used to define filtering criteria for tags, which are untagged packets.

In this Virtual Local Area Network, the layer-3 protocol is carried by the frame to determine VLAN membership. It works in multi-protocol environments. This method is not practical in a predominately IP based network.

3- MAC Based VLAN

MAC Based VLAN allows incoming untagged packets to be assigned virtual LAN and, thereby, classify traffic depending on the packet source address. You define a Mac address to VLAN mapping by configuring mapping the entry in MAC to the VLAN table.

This entry is specified using source Mace address proper VLAN ID. The configurations of tables are shared among all device ports.


Difference between LAN and VLAN

Here is an important difference between LAN and VLAN:

Advantages of VLAN

Here are the important pros/benefits of VLAN:

  • It solves a broadcast problem.
  • VLAN reduces the size of broadcast domains.
  • VLAN allows you to add an additional layer of security.
  • It can make device management simple and easier.
  • You can make a logical grouping of devices by function rather than location.
  • It allows you to create groups of logically connected devices that act like they are on their own network.
  • You can logically segment networks based on departments, project teams, or functions.
  • VLAN helps you to geographically structure your network to support the growing companies.
  • Higher performance and reduced latency.
  • VLANs provide increased performance.
  • Users may work on sensitive information that must not be viewed by other users.
  • VLAN removes the physical boundary.
  • It lets you easily segment your network.
  • It helps you to enhance network security.
  • You can keep hosts separated by VLAN.
  • You do not require additional hardware and cabling, which helps you to saves costs.
  • It has operational advantages because of changing the IP subnet of the user is in software.
  • It reduces the number of devices for particular network topology.
  • VLAN makes managing physical devices less complex.

Disadvantages of VLAN

Here are the important cons/ drawbacks of VLAN:

  • A packet can leak from one VLAN to another.
  • An injected packet may lead to a cyber-attack.
  • Threat in a single system may spread a virus through a whole logical network.
  • You require an additional router to control the workload in large networks.
  • You can face problems in interoperability.
  • A VLAN cannot forward network traffic to other VLANs.
This topic was modified 2 months ago 2 times by Allahgol Alizadah


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