What are VLANs and how do they work?

What are VLANs and how do they work?

What are VLANs and how do they work?

 If you are learning the basics of networking, you will definitely not miss the name VLAN. Maybe now you are confused about what VLAN is. In this post, we will explain to you what a VLAN is and how it works.

What are VLANs?

VLAN (Virtual LAN) is a subnetwork that can group devices on separate physical Local Area Networks (LANs). LAN is a group of computers and devices that share communication lines or wireless links to servers within the same geographic area.

VLANs make it easy for network administrators to partition a network of single switches to suit the functional and security requirements of their systems without having to run new cables or make major changes in their existing network infrastructure. VLANs are often created by larger businesses to repartition devices for better traffic management.

VLANs are also important because they can help improve the overall performance of a network by grouping the devices that communicate most frequently. VLANs also provide security on a larger network by allowing a higher level of control over which devices have access to each other.

VLANs tend to be flexible because they are based on logical, not physical, connections. One or more manageable switches can support multiple VLANs, creating a Layer 2 (data link) subnet implementation. VLANs are associated with broadcast domains. Usually consists of one or more manageable switches

History of VLANs

In the old days before switches and VLANs existed, Ethernet networks were connected through hubs. Hubs put all network hosts onto a single ethernet segment. It's a bit like chaining each host to the next. This is still an improvement over the older token-bus network. At least the host failure didn't cause a chain break.

One major limitation for hubs is that all hosts are in the same collision domain. This means that if two hosts are transmitting at once, data can 'collide', and must be retransmitted. Switches were introduced to solve this, as each port becomes an individual collision domain.

Basic switches, called 'unmanaged switches' have only a simple function. They don't have configurable VLAN support. This means that all hosts on the switch are still part of the same broadcast domain. Meanwhile, managed switches allow traffic separation by using VLANs. In 2003, Ethernet VLANs were described in the first edition of the IEEE 802.1Q standard.

VLAN Type Type

* Protocol VLAN- which handles traffic based on its protocol. The switch will segregate or forward the traffic based on the traffic protocol.

* Static VLAN- Commonly referred to as port-based VLAN, requires a network administrator to assign a port on a network switch to a virtual, temporary network.

* Dynamic VLAN- allows network administrators to define network membership based on device characteristics, instead of switching port locations.

VLAN Port Type Type

Untagged VLANs

Switchports can be 'Tagged' or 'Untagged' ports. An untagged port, or access port on a switch, is connected to a host (such as a server). The connected host sends its traffic without any VLAN tags on the frame. When the frame reaches the switch port, the switch adds a VLAN tag.

The switch port is configured with a VLAN ID that will be included in the tag. Most switchports will use this mode by default, with VLAN ID 1. When a frame leaves an untagged port, the switch strips the VLAN tag of the frame. Traffic is continuing as usual.

Untagged VLAN Ports

Tagged VLANs

Another type of VLAN port is a 'tagged port' when the interface expects a frame that contains a VLAN tag. An example of this is when two switches are connected, and pass tagged traffic. The switch will use the term 'trunk' to refer to the tagged port. The sender will send the frame with a VLAN tag.

The receiving switch will see the VLAN tag, and if VLAN is allowed, it will forward the frame as required. For example, broadcasts may be received on VLAN 10. In this case, the switch will flood frames to all other ports configured with VLAN 10.

VLAN Port Tagged

Native VLANs

In some cases, untagged frames will arrive on tagged ports. To deal with this, tagged ports have a special VLAN configured on them which is called the untagged VLAN. This is also known as 'Native VLAN'. The switch assigns any untagged frames that arrive on a tagged port to the Native VLAN. If a frame on the native VLAN leaves the trunk port (tagged), the switch untags the VLAN. In short, a native VLAN is a way to carry untagged traffic across one or more switches.

Bringing tagged traffic has its uses. This occurs when one switch wants to send information to another switch. Also known as switch-to-switch communication, it is used to share information about connected devices. In this case, if there is a trunk link between two switches, will the sending switch decide which VLAN to use? In short, it sends untagged traffic, which is on the native VLAN.

How VLANs Work

Each VLAN configured on an Ethernet switch can perform address learning, forwarding, filtering, and loop elimination mechanisms such as a separate physical bridge. This allows network administrators to group hosts together even if the hosts are not directly connected to the same network switch.

For example, VLANs can be used to segregate traffic within a business so that users or low priority traffic cannot directly affect the rest of the network's functionality. Many Internet hosting services use VLANs to separate their customers' private zones from one another, allowing each customer's servers to be grouped together in a single network segment while located anywhere in their data center.

You can define one or more virtual bridges on a switch. Each virtual bridge you create on the switch refers to a new broadcast domain (VLAN). Traffic cannot pass directly to another VLAN (between broadcast domains) inside a switch or between two switches. To connect two different VLANs, you can use a router or a Layer 3 switch.

When do you need a VLAN?

* You have more than 200 devices in your LAN

* You have a lot of broadcast traffic on your LAN

* The users group needs more security or is being slowed down by too many broadcasts

* User groups must use the same broadcast domain because they run the same application. An example is a company that has a VoIP phone. Users who use the phone can use a different VLAN, not with ordinary users.

* To make one switch into multiple virtual switches.

Advantages of VLANs

1. Security is guaranteed

2. Cheaper cost

3. Better network performance

4. Reducing the size of the broadcast domain

5. Make device management easier

Lack of VLANs

1. Management is complex

2. Understandable issues in interoperability

3. VLANs cannot forward traffic to other VLANs. A router is required to communicate between VLANs

4. Limited to 4,096 VLANs per switching domain


So what are VLANs? VLAN is a logical group of workstations, servers and network devices that appear to be on the same LAN. VLANs allow multiple networks to work virtually as one LAN.

One of the most beneficial elements of VLANs is eliminating network latency, which saves network resources and improves network efficiency.

Additionally, VLANs are created to provide segmentation and assist in issues such as security, network management and scalability. Traffic patterns can also be easily controlled using VLANs.

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Resa Risyan

Just an ordinary person who wants to share a little knowledge, hopefully the knowledge I provide can be useful for all of us. Keep in mind! Useful knowledge is an investment in the afterlife.

Also, read the article about What Is VoIP And How Does It Work. And see you in another article. Bye
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