Virtual local area networks, or VLANs, have become important as network complexity has exceeded the capacity of typical local area networks (LANs). Originally, a LAN connected a group of computers and associated devices to a server via cables in a shared physical location (hence the term “local”). Many LANs now connect devices via wireless internet, rather than Ethernet, although most LANs use a combination of both connectivity types. Over time, organizations have grown in their networking needs, requiring solutions that enable networks to grow in size, flexibility, and complexity.

VLANs circumvent the physical limitations of a LAN through their virtual nature, allowing organizations to scale their networks, segment them to increase security measures, and decrease network latency.

What is a VLAN and what is its purpose?

In essence, a VLAN is a collection of devices or network nodes that communicate with one another as if they made up a single LAN, when in reality they exist in one or several LAN segments. In a technical sense, a segment is separated from the rest of the LAN by a bridge, router, or switch, and is typically used for a particular department. This means that when a workstation broadcasts packets, they reach all other workstations on the VLAN but none outside it.

This simplifies many of the potential complications caused by LANs, including excessive network traffic and collisions. When two workstations send data packets at the same time on a LAN connected via a hub, the data collides and is not transmitted properly. The collision propagates through the entire network, meaning that the LAN is busy and requires users to wait until the collision has been fully transferred throughout the network before it is operable again—at which point the original data must be resent.

VLANs reduce the incidence of collisions and decrease the number of network resources wasted by acting as LAN segments. Data packets sent from a workstation in a segment are transferred by a bridge or switch, which will not forward collisions but will send on broadcasts to every network devices. For this reason, segments are called “collision domains” because they contain collisions within the bounds of that section.

However, VLANs have more functionality than even a LAN segment because they allow for increased data security and logical partition. Remember, a VLAN acts as a single LAN although it only makes up a segment. This means that the broadcast domain of a VLAN is the VLAN itself, rather than each network segment. Additionally, the partitions do not have to be defined by the physical location of the network devices. They can be grouped instead by department, project team, or any other logical organizational principle.

Why would you use a VLAN?

Organizations benefit greatly from the advantages of VLAN usage, including increased performance, more flexibility in network configuration and workgroup formation, and reduced administrative efforts.

• VLANs are cost-effective, because workstations on VLANs communicate with one another through VLAN switches and don’t require routers unless they are sending data outside the VLAN. This empowers the VLAN to manage an increased data load because, while switches have fewer capabilities than a router, routers cause bottlenecks. VLANs do not need to forward information through a router to communicate with devices within the network, decreasing overall network latency.
• VLANs offer more flexibility than nonvirtual networking solutions. VLANs can be configured and assigned based on port, protocol, or subnet criteria, making it possible to alter VLANs and change network design when necessary. Furthermore, because VLANs are configured on a basis outside their physical connection to hardware or proximity to other devices, they allow for groups who collaborate—and presumably transfer a great deal of data to one another’s devices—to share a VLAN even if they work on separate floors or in different buildings.
• VLANs decrease the amount of administrative oversight required by network overseers like managed services providers (MSPs). VLANs allow network administrators to automatically limit access to a specified group of users by dividing workstations into different isolated LAN segments. When users move their workstations, administrators don’t need to reconfigure the network or change VLAN groups. These factors decrease the amount of time and energy administrators must devote to configuration and security measures.

VLAN Ranges

Here are the important ranges of VLAN:

Virtual LAN (VLAN) is created on Layer 2 switch to reduce the size of broadcast domain. It is one of the technologies used to improve network performance by the separation of large broadcast domains into smaller ones.

There are 5 main types of VLANs depending on the type of the network they carry:

1. Default VLAN –
   When the switch initially starts up, all switch ports become a member of the default VLAN (generally all switches have default VLAN named as VLAN 1), which makes them all part of the same broadcast domain. Using default VLAN allows any network device connected to any of the switch port to connect with other devices on other switch ports. One unique feature of Default VLAN is that it can’t be rename or delete.
2. Data VLAN –
   Data VLAN is used to divide the whole network into 2 groups. One group of users and other group of devices. This VLAN also known as a user VLAN, the data VLAN is used only for user-generated data. This VLAN carrying data only. It is not used for carrying management traffic or voice.
3. Voice VLAN –
   Voice VLAN is configured to carry voice traffic. Voice VLANs are mostly given high transmission priority over other types of network traffic. To ensure voice over IP (VoIP) quality (delay of less than 150 milliseconds (ms) across the network), we must have separate voice VLAN as this will preserve bandwidth for other applications.
4. Management VLAN –
   A management VLAN is configured to access the management capabilities of a switch (traffic like system logging, monitoring). VLAN 1 is the management VLAN by default (VLAN 1 would be a bad choice for the management VLAN). Any of a switch VLAN could be define as the management VLAN if admin as not configured a unique VLAN to serve as the management VLAN. This VLAN ensures that bandwidth for management will be available even when user traffic is high.
5. Native VLAN –
   This VLAN identifies traffic coming from each end of a trunk link. A native VLAN is allocated only to an 802.1Q trunk port. The 802.1Q trunk port places untagged traffic (traffic that does not come from any VLAN) on the native VLAN. It is a best to configure the native VLAN as an unused VLAN.