What are VLANs? Is it necessary to use it? How to create VLANs?

You’ve heard of VLANs or virtual LANs. So what is VLAN? Is it necessary? Find out with lassho.edu.vn’s good experience in the article below!

What are VLANs?

a. What is LAN?

Before learning about VLANs, we must understand what LAN is.

LAN is a local area network (short for Local Area Network), which is defined as all computers in the same broadcast domain.

Routers (routers) intercept broadcasts, while switches (switches) just forward them.

b. What are VLANs?

VLAN is a virtual LAN. Technically, a VLAN is a broadcast domain created by switches. Normally, the router plays the role of creating the broadcast domain. For VLANs, the switch can create a broadcast domain.

You can understand more easily that VLAN is used to divide a switch into many smaller and completely independent switches.

For network : VLAN = Broadcast domain= Logical Network , and for switch : VLAN = Logical switch.

A switch can create multiple VLANs, when the switch has a broadcast sent by a device in one VLAN will be forwarded to other devices in the same VLAN, but the broadcast will not be forwarded to devices in the other VLAN. .

VLAN classification

There are three main types of VLAN networks:

• Port – based VLAN : is a simple and common way to configure VLANs. Each switch port is attached to a specific VLAN (VLAN 1) by default, so any host device attached to that port belongs to a certain VLAN.
• MAC address based VLAN : This configuration is rarely used due to many inconveniences in management. Each MAC address is marked with a specific VLAN.
• Protocol-based VLAN : This configuration is similar to MAC Address based, but uses a logical address or IP address instead of the MAC address. The configuration is no longer common by using the DHCP protocol.

Are VLANs necessary?

You need VLANs when your computer network is too large and has too much traffic.

Another important issue is that on Cisco switches, VLANs are enabled by default and all computers are in one VLAN. That VLAN is VLAN 1. So by default, you can use all ports on the switch and all computers are able to communicate with each other.

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Benefits of VLANs

– Save network bandwidth: Because VLAN can divide LAN into different segments.

– When sending a packet, it will only send in a single VLAN, not in other VLANs, so it can reduce traffic, save bandwidth, and do not reduce transmission speed.

– Increased security: Different VLANs cannot access each other (unless there is a routing declaration). If there is a failure of one VLAN, it will not affect the other VLAN.

– Easily add or remove computers to VLAN: On a multi-port switch, it is possible to configure different VLANs for each port, so it is easy to connect more computers with VLANs.

– Network with high mobility: VLAN can easily move devices. VLANs can be configured statically or dynamically. In the static configuration, the network administrator must configure each port of each switch. Then assign it to a certain VLAN. In dynamic configuration, each port of the switch can configure its own VLAN based on the MAC address of the device it is connected to.

VLAN network brings a lot of benefits to help reduce the load and evenly distribute internet access, especially for computers with large capacity, many people accessing at the same time so that users can access the internet faster. VLAN networks are often applied to large companies when the amount of internet traffic is too much at the same time.

When do you need a VLAN?

You need to consider using VLANs in the following cases:

– You have more than 200 computers in the LAN.

– Broadcast traffic in your LAN is too large.

– Workgroups that need increased security or are slowed down by too many broadcasts.

– Workgroups need to be on the same broadcast domain because they are sharing the same applications. For example, a company uses VoIP phones. Some people who want to use the phone may be on a different VLAN network, not with regular users.

– Convert a single switch into multiple virtual switches.

How to create VLANs? What do VLANs provide?

a. How to create VLANs?

How to configure a VLAN network can vary depending on different Cisco switch models. Your goal is:

• Create a new VLAN.
• Set each port to the appropriate VLAN.

Let’s say we want to create VLANs 5 and 10. We want to put ports 2 and 3 into VLAN 5 (Marketing) and ports 4 and 5 into VLAN 10 (HR). Here’s how to do it on a Cisco 2950 switch:

At this time, only ports 2 and 3 can communicate with each other as well as only ports 4 and 5 can communicate with each other. The reason is because they are on the same VLAN. In order for the computer on port 2 to communicate with the computer on port 4, you need to configure the trunk port to the router so that it can remove VLAN information, route packets, and add VLAN information.

b. What do VLANs provide?

VLAN helps to increase the performance of medium and large LANs because it limits broadcast messages. As the number of computers and traffic increases, the number of broadcast packets also increases. By using VLANs, you can limit broadcasts.

VLANs also enhance security because you essentially put a group of computers in a VLAN on their own network.

The above article briefly introduces VLAN or virtual LAN. Hope it helps you in the process of using the computer!