What is VLAN in Networking?

Virtual Local Area Network (VLAN) is a local network that combines a number of machines in a logical and non-physical way. It was developed by IEEE and runs on OSI Layer 2 layer.

VLAN Nedir? Ne İşe Yarar?

What is VLAN?

Today, physical networks are often based on one or more devices that manage data traffic between devices. To do this, all network cables are connected to the switch that allows different computers to communicate. Then hundreds of these switches ensure a relatively smooth communication when connecting the devices together. However, it may be appropriate to break down these large networks without changing anything in the physical facility.

A Virtual LAN is a smaller logical partition created within a large physical network made by connections. The spread of the local network to several switches is not a problem here. All that matters is that the key is compatible with a VLAN. Only managed switches can create virtual LANs.

The distribution of packets therefore passes directly through the switches. Administrators define which virtual ports belong to different ports on them. The Virtual LAN is therefore static. If VLANs need to be grouped differently, the ports must be redistributed in the switch configuration.

However, each port can only be part of a single VLAN. If devices in a VLAN need to communicate with another VLAN, this communication must be done through a router that can transmit message packets, as for communication between a home network and the Internet.

Under normal circumstances, there is always one Virtual LAN in a manageable Switch. This VLAN is called a Native VLAN. Each client plugged into the switch ports automatically subscribes to the Native VLAN and can communicate with each other. The Native VLAN is configured as VLAN1 on each Switch by default.

What is a Tagged VLAN?

In the case of a labeled Virtual LAN, assignment to VLANs is more dynamic: instead of being defined in the key, the allocation is made on a label on the label of the VLAN. That’s why we call this technique VLAN per port. The tag identifies the VLAN we are in, and a switch can identify which segment of the communication is taking place and transmit the message.

A VLAN tag has 32 bits and appears directly after the sender’s MAC address in the Ethernet frame. The tag starts with 16 bits to identify the protocol: The Tag Protocol Identifier (TPI) indicates whether a VLAN ID is populated. If a Virtual LAN is marked with a frame, these blocks are 0x8100.

The next three bits of the frame indicates the priority of the message. They follow a bit for the Canonical Format Identifier (CFI). This field is only used to ensure compatibility between Ethernet addresses and the token ring.

Only in the last twelve bits, the protocol refers to the actual identifier of the virtual local area network (VID). The length of this field allows 4,096 different VLANs. Each virtual LAN receives its own number. It is also possible to implement tagged VLANs directly over network cards. For example, Linux supports this default standard. However, for Windows users, it depends on the network card manufacturer. It can then be configured using the device driver.

The frame principle presented here follows the IEEE 802.1q standard. This is the most commonly used variable, but there are other possibilities to place VLAN tags in a message package. For example, Cisco uses the Switch-to-Switch Connection Protocol (ISL) for switches. To allow multiple Virtual LANs, this protocol includes the entire data frame.

The advantage of a labeled VLAN over a VLAN with a port assigned is the connection between multiple switches. In the case of VLANs per port, at least two wires must be connected between the switches, since each VLAN requires its own cable. In the case of housings in labeled VLANs, one cable is sufficient since the distribution is made using frame information. The key identifies the VLAN and transmits it to the second key. The label is then removed and the package is sent to the correct recipient.

What Does It Do?

Since the VLAN supports a broadcast domain, each structure is considered a network. Within a business, the task units are located separately within the building. For example; Suppose that there are 3 rooms of the same unit (Research) on the Floors1, Floors2, and Floors3 of the building.

VLAN is used to transmit data between units operating in different locations. For example, the following image shows you a network topology that is designed by creating a VLAN on Cisco Switches.

Configuring VLANs in Packet Tracer

In the image above there are different VLAN users on each floor. According to this network topology, implementing the Virtual network in Cisco Switch is the most logical way.


The advantage of using a Virtual Local Arae Network may vary according to the network topology. The main advantages are;

1. Each VLAN is a broadcast domain.
2. When a client sends a broadcast frame, only members of that Virtual LAN receive the broadcast frame.
3. A user who is a member of a created Virtual LAN cannot communicate with other VLANs.
4. Based on the above image, an IT employee can be accommodated on each floor.
5. To avoid unnecessary busy network traffic, devices such as the Printer can be made members of different VLANs.
6. A different Virtual LAN can be created for IP VoIP (Voice over IP) phones.
7. Wireless guest networks can be created using Wireless Access Point network devices that support VLANs.

Configuration ⇒ Video

You can watch the video below for VLAN configuration using Packet Tracer and also subscribe to our YouTube channel to support us!

   Final Word

In this article, we have reviewed the Virtual LAN that allows us to use local networks more efficiently on Cisco or another brand of Switch. Using this structure, you can significantly increase your network traffic. Thanks for following us!

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