What is VLAN (Virtual Local Area Network)?

In modern network infrastructure, VLAN (Virtual Local Area Network) plays a vital role in organizing data traffic. It also ensures that networks operate more efficiently and effectively. The VLAN network developed by IEEE functions at OSI Layer 2. In short, we use this technology to separate our physical networks into logical networks.

If I clarify my statements, VLAN creates non-physical networks. As a result, we facilitate the organization and management of networks. In this professional article, I will describe exactly what virtual LANs are and their basic concepts.

What is VLAN (Virtual Local Area Network) or Virtual LAN?

Virtual Local Area Network (VLAN) combines machines, namely devices, logically and virtually. This technology, developed and marketed by IEEE, works at OSI Layer 2.

Today, physical networks manage data traffic between devices. For this, all network cables are connected to the switch that allows devices to communicate.

Switches perform communication by connecting hundreds of devices. Therefore, we need to divide large networks into smaller groups. At this point, we can do this without changing the physical layout.

Virtual LAN creates a logical division within an extensive physical network. This does not cause a problem in local networks spread over multiple switches. The important thing is that the switch supports virtual LANs. In other words, we can create these virtual LANs on managed switches.

In addition, the distribution of packets passes directly through the switch. System administrators determine which ports belong to which VLAN. Obviously, these groups are static.

If we change the grouping, we need to reconfigure the ports. For example, a port can only be part of one VLAN.

If the devices will communicate with different VLANs, we can do this through a router. For example, it is similar to the communication between home networks and the Internet.

Usually, there is a Virtual LAN on each managed switch. In fact, we also call it Native VLAN.

Every client connected to the switch automatically joins the Native group. These clients can communicate with other devices. By default, we refer to this group as VLAN1.

What is Tagged VLAN?

In the case of a tagged VLAN, the assignment to groups is more dynamic. That is, we do not define it in the switches. Instead, we do it in a VLAN tag.

We can also call this technique “VLAN per port.” That is, the tag specifies the relevant group you are in. So, the switch can forward the message by understanding which segment the communication is in.

Also, a VLAN tag has 32 bits. It appears right after the sender’s MAC address in the Ethernet frame.

In addition, the tag starts with 16 bits to identify the protocol. The Tag Protocol Identifier (TPI) indicates whether an ID is filled in or not. If the frame is tagged, this block takes the value 0x8100.

The next three bits of the frame specify the priority of the message. Then, one bit is for the Canonical Format Identifier (CFI). This bit ensures compatibility between Ethernet addresses and the token ring.

Finally, the last twelve bits define the virtual local area network (VID). This field allows for 4,096 different VLANs. For this reason, each virtual LAN gets a unique number.

In addition, we can also make tagged VLANs via network cards. For example, Linux supports this standard by default. However, Windows users are dependent on the network card manufacturer. If we decide, we can configure it via the device driver.

The framework presented here follows the IEEE 802.1q standard. This is the most widely used variant. However, there are other methods to add group tags to packets.

For example, Cisco products use the Inter-Switch Link Protocol (ISL). This protocol includes the entire data frame to allow multiple VLANs.

As a result, tagged groups have an advantage over those with ports assigned. It is easier to establish connections between multiple switches.

In a per-port VLAN, each group requires its own cable. However, in a tagged structure, a single cable with the frame information is sufficient. In this case, the switch recognizes the VLAN and forwards it to the other device. Then, it removes the tag and delivers the packet to the correct recipient.

What is the Use of VLAN & Virtual LAN?

Since virtual LANs support broadcast domains, we consider each structure created as a network. Within a business, we position the task units separately within the building. For example, Let’s assume that there are 3 rooms from the same unit (Research) on Floor 1, Floor 2, and Floor 3 of the building.

Virtual LAN comes into play for data transmission between units working in different locations. For example, the image below shows you a network topology designed by creating VLANs on Cisco Switches.

Since there are different LAN groups on each floor in the image above, it is necessary to use VLANs in such a structure.

VLAN Advantages and Disadvantages

Virtual LANs optimize network performance by segmenting traffic. However, while they offer some advantages, they also present challenges. Let’s explore the advantages and disadvantages of utilizing this structure.

1) Pros

• Advanced Security

VLANs provide adequate security by separating network traffic. They also logically group users and resources. This reduces the risk of unauthorized access.

• Improved Network Performance

Virtual LAN provides efficient traffic management by reducing network congestion. Plus, it optimizes performance and reduces latency by separating broadcast domains.

• Simplified Network Management

VLAN networking simplifies LAN management. It also simplifies network changes and reduces the impact of broadcast storms. This helps us increase overall network scalability.

• Flexibility and Scalability

It makes it easy to adapt to network requirements. It also scales the infrastructure without the need for physical reconfiguration. In short, it is straightforward for us to add new users or departments.

2) Cons

• Complex Configuration

Organizing and maintaining a virtual LAN structure may seem complicated. You also need to plan and manage member assignments carefully. So, this process is sometimes time-consuming and challenging.

• Increased Network Load

VLANs can add additional load to your network structure. Additionally, increased use of network devices and the need for routing between groups can impact performance.

• Potential Security Risks

You can increase security by using virtual networks. However, there is a risk of misconfiguration and bypass attacks. As a result, insufficient segmentation can lead to security threats.

• Limited Broadcast Area

Virtual networks sometimes result in limited broadcast domains. This also creates additional complexity in managing broadcast traffic. To address this, you must perform further fine-tuning for broadcast-intensive applications.

How Do VLANs Manage Broadcast and Communication Between Different Domains?

VLANs, which work most effectively in managing network traffic, also manage different structures.

1) How Do VLANs Manage Broadcast?

• Broadcast Limitation

VLANs limit broadcast traffic within their boundaries. Obviously, this reduces unnecessary traffic propagation.

• Broadcast Areas

Each VLAN creates a separate broadcast domain, thus reducing network congestion and improving data throughput.

• Broadcast Filtering

VLANs forward broadcasts only to connections within the same ID. In short, it prevents unnecessary port usage.

2) How Do VLANs Enable Communication Between Other Groups?

• Inter-VLAN Routing

It uses inter-VLAN routing to provide communication between groups. In summary, you can do this with a Router or a Layer 3 Switch.

• Router Configuration

You need to configure the router with subinterfaces or dedicated physical interfaces for each VLAN, which will create logical connectivity between VLANs.

• Layer 3 Switching

Layer 3 switches perform routing functions at the hardware level. Therefore, they provide faster and more efficient data transfer.

• VLAN Trunk

We use VLAN trunk with protocols like IEEE 802.1Q. In fact, it transmits multiple virtual LAN traffic over a single connection.

The role of VLANs in broadcast management is essential. Therefore, it provides us with network efficiency, security, and scalability. As a result, it effectively limits broadcast traffic. Thus, it provides controlled communication between different groups.

What are Tagged and Untagged VLANs, and What are the Differences?

If we want to expand our VLAN network knowledge, we need to know some details. In particular, these are Tagged and Untagged VLAN types.

We also know the Untagged VLAN type locally. In other words, this is actually the default. We can connect our devices without making any settings.

When a device is attached to an untagged VLAN, the switch automatically assigns frames to this group. In addition, devices in the same untagged group can communicate without virtual network information.

We use Tagged VLAN for our devices that are sensitive to groups. For example, if we configure a switch device for a specific tagged VLAN, we add tags to the frames. Thus, we connect our devices regardless of their physical location. In short, we can communicate with other devices in the same group, that is, with IDs.

For these reasons, it is vital to understand the difference between tagged and untagged VLANs. With this information, we provide the correct VLAN configuration. As a result, we separate our traffic appropriately.

What are the Usage Areas of Tagged and Untagged VLANs?

For a tagged VLAN network, we usually decide to use it to carry traffic between switches. If we connect multiple switches, we can route traffic correctly between switches thanks to the tagged structure.

So, we add tags to each frame. The switches distinguish between VLANs so that they reach the right destination.

An untagged VLAN network is usually ideal for endpoint devices. For example, we can exclude computers, printers, and other devices, such as our IP phones, from the management network. We only allow devices with administrative access by making them members of a tagged group.

Let me give an example of a real-world scenario; first, let’s consider an office network.

• We have two switches: central and access. On our main switch, the trunk ports carry traffic tagged with VLAN 10 (Finance) and VLAN 20 (HR).
• Our access switch connects VLANs 10 and 20 to the main switch via the trunk port.
• We connected the PCs in the finance department to the ports that we made members of VLAN 10. In this case, these ports send untagged traffic.

In summary, tagged VLAN refers to the trunk connection between the primary and access switch. On the other hand, untagged VLAN refers to the untagged port for finance PCs.

Virtual LAN Configuration ⇒ Video

You can oversee our video tutorial below to configure Virtual LAN using Packet Tracer. Plus, you can join our YouTube channel to support us wholeheartedly!

Frequently Asked Questions (FAQ) About VLAN

1. What is VLAN?

VLAN, or Virtual Network, is a method of dividing a physical network into multiple virtual LANs. This method provides better organization and security within the network. It also improves traffic management.

2. What are the benefits of using VLANs?

Virtual LANs increase security by isolating data and reducing broadcast traffic. In other words, they group devices independently of their locations. However, they offer a more flexible structure.

3. How does segmentation work?

We do this by assigning ports on network switches to separate virtual networks. That is, devices in the same group communicate with each other as if they were on a physical network. However, we need a Router or L3 Switch to communicate between VLANs.

4. What are the different types of VLANs?

There are two main types of virtual networks: port-based and 802.1Q. In a port-based system, we assign specific ports to a group. In contrast, in an 802.1Q system, we define groups with tags in frames.

5. What is the purpose of a native VLAN?

We actually use the local virtual LAN type for untagged traffic on the trunk link. Therefore, we usually prefer it for management traffic and untagged devices.

6. Can it cover more than one switch?

Yes, we need to cover many switches and also make the trunk connections correctly. In addition, we can carry VLAN traffic with this structure throughout the network.

Conclusion

To summarize everything, the VLAN network provides a powerful solution to optimize our infrastructure. It also improves security and facilitates communication within complex physical structures. For these reasons, we need to understand the principles of virtual LANs.

Moreover, with this network technology, we can minimize broadcasts. Thus, we achieve higher LAN performance. After all, as technology advances, such methods will continue to play a critical role.