VLANs: How to Implement, Secure, and Manage

Published on: October 3, 2023

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18 min read

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For German Version

As a necessary component of today's network architecture, Virtual Local Area Networks (VLANs), are crucial for enhanced performance and security. Network administrators use them to group devices together based on logical connections rather than physical ones and to manage traffic more effectively and securely. VLANs partition a single switched network into a set of overlaid virtual networks that can meet different functional and security requirements, avoiding the need to have multiple, distinct physical networks for different use cases. VLANs can be used to separate network traffic and limit access to specific network resources, improving security by preventing unauthorized access to sensitive data and network resources.

Segmentation architecture, data integrity protection, and efficient network management are powerful aspects of virtual local area networks. Network managers construct numerous isolated segments inside a single physical network architecture using the virtual zoning technique they offer. This network segmentation empowers controlling data traffic flows, optimizing network performance, and enhancing security by isolating different departments, services, or user groups from each other.

VLANs come with stronger security, ease of use, and an improved user experience when applied properly. VLANs can provide an additional layer of security to protect assets. However, there are security issues that need to be taken into account during design and implementation. Misconfiguration may leave a network vulnerable, and switch vendor implementations have in the past had security issues. Following best practices and security tips in configuration, such as setting up VLANs with department-based divisions and restricting traffic using Access Control Lists (ACLs), will save the day.

The following topics are going to be covered in this article:

• What is a VLAN?
• How do VLANs Operate?
• What benefits and use cases do VLANs offer?
• Which types and configurations of VLANs exist?
• What steps are involved in VLAN implementation?
• How can VLANs be effectively Secured?
• What challenges and considerations arise with VLANs?
• How does Inter-VLAN Routing facilitate communication?
• What is the Difference Between VLAN and Subnet?
• What is the Difference Between VLAN and LAN?
• What tools and solutions aid VLAN Management?
• How can Zenarmor NGFW protect VLANs?
• How can VLANs be configured on OPNsense?
• How can VLANs be configured on pfSense?

What is a VLAN?

A VLAN, or Virtual Local Area Network, is a logical overlay network that groups together a subset of devices that share a physical LAN, isolating the traffic for each group. VLAN does this by being a logical network segment within a physical network infrastructure. VLAN is created by grouping together devices, such as computers, servers, switches, and routers, into a virtual network that appears as if they are all connected to the same physical network, even though they may be physically dispersed across different locations. VLANs function by offering network segmentation, which can enhance management, security, and performance. VLANs can increase security by preventing unwanted access to critical data and network resources by segregating network traffic and limiting access to particular network resources.

VLANs partition a single switched network into a set of overlaid virtual networks that meet different functional and security requirements, avoiding the need to have multiple, distinct physical networks for different use cases. They are defined by software rather than physical wiring, which allows for greater flexibility and control over network traffic. They function by applying tags to network frames and handling these tags in networking systems, creating the appearance and functionality of network traffic that is physically on one network that behaves as though it were divided into multiple networks. They function by assigning a unique identifier, known as a VLAN ID or VLAN tag, to network packets. These tags are added to Ethernet frames as they traverse the network, allowing network switches to identify which VLAN a packet belongs to and make forwarding decisions accordingly.

Applying VLANs to network architecture is essential for modern networks where security, flexibility, and efficient resource utilization are critical. VLANs empower organizations to adapt to changing network requirements while maintaining control and security as the networks and the internet itself grow rapidly.

How do VLANs Operate?

VLANs operate by grouping together a subset of devices that share a physical LAN, isolating the traffic for each group. VLANs work by applying tags to network frames and handling these tags in networking systems, creating the appearance and functionality of network traffic that is physically on a single network but acts as if it is split between separate networks. VLAN tagging is a way to identify and distinguish VLAN traffic from other network traffic, typically done by adding a VLAN tag to the Ethernet frame header. VLAN membership determines which devices are assigned to which VLANs, and devices can be assigned to VLANs based on port, MAC address, or other criteria. VLAN trunking permits several VLANs to be maintained over just one physical link, often utilizing an IEEE 802.1Q protocol. Trunk lines providing VLAN or priority values will be using "tagged" frames.

By default, a trunk port sends traffic to and receives traffic from all VLANs, and all VLAN IDs, 1 to 4094, are allowed on each trunk. However, VLANs can be pruned to limit the number of VLANs that are allowed on a trunk. To configure the list of VLAN IDs to be accepted by the trunk port, the VLAN-id-list statement is included, and the list of VLAN IDs is specified. When a packet with a VLAN ID in the trunk interface list comes in, it is acknowledged and transmitted into the bridge domain that has been set up with the appropriate VLAN ID. VLAN IDs play a crucial role in segregating and organizing network devices by enabling the grouping of devices together based on logical rather than physical connections.

Some necessary terms to understand how VLANs work are outlined below:

• VLAN Membership: Devices on the network are organized into groups based on their VLAN membership. Devices within the same VLAN can communicate with each other as if they were on the same physical network, even if they are located in different physical locations.
• VLAN Tagging: When data is transmitted over the network, each Ethernet frame is tagged with a VLAN identifier, typically a 12-bit VLAN tag. This tag is inserted into the frame's header and specifies the VLAN to which the data belongs.
• Network Switches: Network switches play a crucial role in VLAN operation. They examine the VLAN tags on incoming frames and determine how to forward the frames within the network. Switches maintain VLAN information in their MAC address tables to optimize traffic delivery within VLANs.
• Isolation and Segmentation: VLANs provide network segmentation and isolation. Devices in one VLAN cannot directly communicate with devices in another VLAN unless routing or firewall rules are configured to allow such communication. This isolation enhances security and network control.

What Benefits and Use Cases Do VLANs Offer?

Implementing Virtual Local Area Networks (VLANs) in network infrastructure offers several significant advantages, extending across various facets of network management and operation, including efficiency, performance, and security.

The purpose and advantages of incorporating VLANs into network architecture are outlined below:

• Network Isolation and Security: VLANs allow network administrators to logically segment their network based on departments, functions, or security requirements in a robust way. This isolated traffic significantly improves security and minimizes the risk in the event of a security breach or malware outbreak in one VLAN. The impact is contained within that VLAN, preventing it from spreading to other parts of the network by limiting access to specific network resources. A finance department can be placed on a separate VLAN from the marketing department and ensure that financial data remains inaccessible to marketers, for instance.
• Optimized Traffic Flow: VLANs enable to prioritize and control traffic within each VLAN. This ensures that critical applications or services receive the necessary bandwidth while preventing non-essential traffic from interfering, reducing latency, and providing quality of service (QoS). For instance, in a hospital's critical care unit, voice-over-IP (VoIP) phones can be assigned to a high-priority VLAN to ensure that communication remains uninterrupted, even during periods of network bottleneck.
• Simplified and Efficient Network Management: Network management is simplified by allowing consistent configurations and policies to be applied to groups of devices within a VLAN. Complexity is reduced, network administration tasks are streamlined, and it is easier to maintain and troubleshoot the network because of this. For instance, different VLANs can be established for students in a university campus network, a faculty building, and administrative staff. Network policies, such as internet access restrictions, can be applied more efficiently based on VLAN membership, making it easier to manage network resources and access.
• Flexibility and Scalability: New devices can be assigned to existing VLANs or placed in new ones logically without the need to physically rewire the network, facilitating network expansion and providing flexibility. They let users add or relocate devices within the network without the need for extensive physical rewiring. They can be used to separate web servers, application servers, and database servers in a growing e-commerce business. New servers can be added to the respective VLANs in case the company grows without disrupting the existing infrastructure, ensuring seamless scalability.
• Performance and Resource Optimization: VLANs can be configured dynamically, allowing you to adjust network configurations quickly and easily as needed. They help reduce network congestion and improve network performance by segmenting network traffic and limiting broadcast traffic. By grouping devices with similar communication patterns or requirements, VLANs optimize the use of network resources and bandwidth. This ensures that network resources are used efficiently.
• Compliance and Regulatory Requirements: VLANs can assist in complying with regulatory requirements by ensuring that sensitive data is segmented and protected. This is especially significant in the medical and financial fields. Patient data in a healthcare network can be kept in a dedicated VLAN with strict access controls, ensuring compliance with privacy regulations like HIPAA.
• Broadcast Domain Control: VLANs reduce the size of broadcast domains. In larger networks, this prevents broadcast storms, which can degrade network performance. Smaller broadcast domains lead to more efficient use of bandwidth. On a large university campus with multiple buildings, for instance, each building can be assigned to a separate VLAN. This way, broadcast traffic is contained within each building's VLAN, preventing it from impacting other parts of the network.

Which Types and Configurations of VLANs Exist?

There are different types of VLANs that can be implemented in network architecture, depending on how they are configured and used within a network. The most common VLAN types are as follows:

1. Port-based VLANs: They are often used in small networks and are based on physical ports or interfaces on network switches. Host computers connected to specific ports on a switch are assigned to a specific VLAN, and devices connected to these ports are automatically part of that VLAN. The network switch associates a VLAN ID with each physical port. Devices connected to these ports are unaware of their VLAN membership, as it is configured at the switch level. The setup would be relatively easy but may not provide the flexibility required for complex network scenarios, as it is the simplest type of VLAN.
2. Tag-based VLANs: VLAN membership is determined by tagging Ethernet frames with a VLAN ID in tag-based VLANs, which allows multiple VLANs to coexist on a single physical trunk (link). Multiple VLANs are assigned to a single port, making them more flexible and scalable compared to port-based VLANs. They are a more advanced VLAN type that uses tags to identify which packets belong to which VLAN and are also known as 802.1Q VLANs. Devices on a tagged VLAN can be connected to the same physical switch or multiple switches interconnected via trunk ports. The VLAN ID is included in the Ethernet frame's header, enabling switches to differentiate and route traffic to the correct VLAN based on the tag.
3. Protocol-based VLANs: These VLANs are less common than port-based and tag-based VLANs because they are based on the type of protocol that the traffic is using, such as IP or IPX, rather than a port or tag. They are less common, mostly preferred in specialized scenarios, and require more complex configurations. It is useful for segmenting traffic that doesn't neatly fit into port-based or tag-based VLANs. Network switches classify traffic based on Layer 3 (network layer) protocol information, such as IP addresses or IP subnets. For example, all traffic for a specific IP subnet could be placed into a particular VLAN.
4. Voice VLAN: This is meant for VoIP traffic. It prioritizes voice data over other types of traffic, aiming to have fewer interruptions or delays. Voice VLANs employ Quality of Service (QoS) mechanisms to give preferential treatment to voice packets. They also aim to minimize latency and jitter for clear talks.
5. IP subnet-based VLANs: VLAN membership is determined by the connected device's IP subnet. Devices with IP addresses in a specific subnet are assigned to a corresponding VLAN. This approach aims to simplify network management by aligning VLANs with IP addressing schemes.
6. Management VLAN: Employed to manage switches and routers. It isolates management traffic from user data traffic. The aim is better security and reducing the risk for management interface breaches.

What are the VLAN Configuration Modes?

Other than types, there are different VLAN configuration modes that determine how VLANs operate within a network. The most common VLAN configuration modes are as follows:

1. Access mode: A switch port is assigned to a single VLAN and carries traffic only for that port of the VLAN. It is typically employed to connect end-user devices, such as computers, printers, or IP phones, to a specific VLAN based on their port assignment.
2. Trunk mode: A switch port carries traffic for multiple VLANs by adding VLAN tags to Ethernet frames. It is good to use for interconnecting switches or connecting to a router, in general, to pass traffic from multiple VLANs over a single physical link, especially in scenarios where devices in different VLANs need to communicate.
3. Hybrid mode: This is a combination of access and trunk modes on a single port, letting a switch port carry traffic for both a single VLAN and multiple VLANs, which are untagged (access) traffic and tagged (trunk) traffic. It can be useful when a single port needs to connect both end-user devices (untagged) and other switches or routers (tagged), simplifying the network design. It is mostly employed to connect to a virtualization host.

Understanding these types of VLANs and their configurations is essential for network administrators to effectively design and manage networks, optimize traffic flow, and enhance security by segmenting and controlling network traffic according to needs and requirements. VLANs are practical for these purposes and they are implemented to complete the following tasks:

• Segment a network into smaller, more manageable parts, improving network performance and security
• Prioritize traffic based on the type of data being transmitted, such as voice or video, to improve the quality of service for critical applications
• Provide internet access without compromising the security of the main network for guests by creating separate guest networks
• Enable communication for virtual machines by creating virtual networks while remaining isolated from the main network

What is the Importance of VLAN?

VLANs are more adaptable than the majority of conventional LAN networks, as the connections are logical rather than physical. Items can be grouped in a VLAN to eliminate the need to physically group comparable entities, which could be more work than it's worth. By employing a VLAN to isolate a group that might hold sensitive data from the rest of the network, the likelihood of a possible breach is reduced. Since a VLAN eliminates the need to build connections, costly network upgrades are no longer required.

By splitting the network into several logic domains and eliminating unnecessary traffic, performance is increased. When a network is divided, fewer devices are present in a broadcast domain. VLANs make network management easier by allowing management for a particular device to be enforced based on its logical connections, which are far more flexible than its physical connections. Project management is easier since group members working on the same project are no longer required to be in the same location because a VLAN enables connections in separate locations.

Without VLANs, networks face several challenges that can hinder performance and security. All devices would belong to a single broadcast domain, leading to excessive broadcast traffic. This congestion can overwhelm the network, resulting in degraded performance and increased latency due to broadcast storms. Sensitive information would be more vulnerable as there would be no logical separation between different user groups or departments. Managing a large network without VLANs would require more physical hardware (like switches), making it cost-prohibitive and logistically challenging. More struggle would be needed with device configuration and troubleshooting. Expanding a non-VLAN segmented network would necessitate significant physical changes and reconfigurations, which could lead to downtime and increased operational costs.

What is a VLAN Interface?

A VLAN interface, also known as a Switch Virtual Interface (SVI), is a virtual Layer 3 interface configured on a switch. Unlike physical interfaces, which connect directly to network devices, it represents a VLAN within the switch and provides a means for the switch to participate in Layer 3 functions like routing. It differs from the physical interfaces seen on switches and routers. Rather, it is a switch-created virtual interface that enables traffic routing between many VLANs.

VLAN interfaces come with Layer 3 routing capabilities and enable communication between different VLANs. Each VLAN interface is assigned a unique IP address within its subnet. The switch provides inter-VLAN routing and serves as the default gateway for hosts in that VLAN. VLAN interfaces facilitate remote management of the switch itself. IPs are set to a VLAN interface, and switches can be accessed for configuration and monitoring via Telnet, SSH, or HTTP. It can perform Layer 3 switching or routing. The switch can forward traffic between VLANs based on IP addresses, rather than just MAC addresses. There is less need to send traffic to a separate router for inter-VLAN communication. VLAN interfaces simplify network design. A single switch can handle both Layer 2 switching inside VLANs and Layer 3 routing between VLANs. Separate routers or complex topologies are not needed anymore. It segments traffic into different VLANs and provides extra security, in addition to broadcast traffic reduction.

What is a VLAN Subinterface?

A VLAN subinterface is a logical division of a physical interface on a router or a Layer 3 switch. At the network level, a virtual or physical interface can be logically divided into VLAN subinterfaces. Layer 3 interfaces that receive and transmit 802.1Q VLAN tags are called VLAN subinterfaces. It handles multiple VLANs through a single physical connection. A single virtual interface can have more than one VLAN tag assigned to it. The packet's associated VLAN tags indicate which VLAN the packet flows to when it reaches that interface. Traffic can be routed to several VLANs for your services using VLAN subinterfaces. Each subinterface can be assigned its own IP address, subnet mask, and VLAN ID. Now the router can route traffic between different VLANs in an efficient way. This configuration is known as router-on-a-stick. A single physical interface is employed to route traffic for multiple VLANs using 802.1Q encapsulation. They tag frames with their respective VLAN IDs. VLAN subinterfaces contribute significantly to the functionality of VLANs in several ways:

• Inter-VLAN Routing: Routing between different VLANs is enabled. Each subinterface corresponds to a specific VLAN and handles communication between them.
• Efficient Use of Resources: Saving hardware costs and physical ports. Instead of separate interfaces for each VLAN, one physical connection is enough.
• Simplified Configuration: Simplifying the network design, configuration, and management process of complex networks with numerous VLANs. Each subinterface can be configured independently with its own IP addressing and routing policies.
• Security and Scalability: Implementing Access Control Lists (ACLs) or firewall rules on each logical interface. As networks grow and require more VLANs, additional VLANs can be added without the need for extra physical interfaces.

What is VLAN Segmentation?

VLAN segmentation restricts malicious actors to access to assets and benefits linked to the subnet that corresponds to the target device. VLANs offer flexibility in organization and segmentation. Based on logical connections, a collection of devices in a VLAN interact as though they were connected to the same line. VLANs enable an administrator to divide networks according to criteria like function, project team, or application. This can be done without taking into account the actual location of users or devices. Even though devices in a VLAN share infrastructure with other VLANs, they behave as though they are in a separate network. Unicast, broadcast, and multicast packets are only forwarded and flooded to end stations within the VLAN where they are sourced, and any switch port can be a part of a VLAN.

Broadcast domains are isolated via VLAN. In this manner, rather than being exposed to the entire network, broadcasting network activity is kept within a specific segment. This maximizes efficiency by lowering the likelihood of unneeded server overload and network congestion during peak hours. VLANs are Layer 2 divisions. So VLANs must be employed when the decision is to divide a network at a data link. Although many networks may not be linked to the same fiber switch, they can coexist on the same physical network thanks to VLAN.

VLAN segmentation forms a group of separate networks inside the data center. Every network is a broadcast domain of its own. VLAN segmentation significantly reduces access to system attack surfaces when set up correctly. It raises threat agent effort and decreases packet-sniffing capabilities. The servers and other equipment required to carry out their everyday duties are visible to permitted users.

Protocol separation is an additional benefit of segmentation. Network architects have the ability to restrict specific protocols to particular business units. Communication systems on your line may have their own VLAN. This restricts each VLAN's traffic to pertinent packets. Network segmentation by VLANs allows for safe, adaptable user mobility. For instance, no matter where they are, a user assigned to a particular VLAN will always connect to that VLAN. This is especially useful for creating wireless limitations.

How Does VLAN Segmentation Contribute to Network Performance?

By merely dividing a bigger network into pertinent segments, VLANs reduce network congestion. By doing this, VLANs lessen the strain on individual devices to respond to these incessant background inquiries. They focus only on the pertinent traffic and save resources. When a device sends a broadcast frame, only devices within the same VLAN receive it. From the standpoint of an administrator, it is feasible to limit or restrict the bandwidth utilization of each subnet, which aids in regulating the use of resources that have been purchased. VLANs divide networks based on functional requirements. They give priority to traffic flow inside each VLAN. Each VLAN forms its own broadcast domain. This means that broadcast traffic, such as ARP requests or DHCP broadcasts, is confined within the specific VLAN. This prevents unnecessary broadcast traffic from flooding the entire network. Distinct VLANs for data and voice traffic can be employed for performance and security concerns. Voice packet security demands the same level of attention to detail as data VLAN security. To further prevent performance problems, VLAN QoS tagging makes sure switches handle voice traffic first.

How Does VLAN Contribute to the Efficiency of Network Traffic Management?

Network traffic management is the process of monitoring, controlling, and optimizing the flow of data across a network. It involves various techniques to ensure efficient data transmission, prevent congestion, and prioritize critical traffic.

VLANs provide a powerful tool for network traffic management. It achieves this by reducing broadcast traffic, prioritizing critical traffic, isolating traffic, and simplifying network management. Unnecessary broadcast traffic can't flood the entire network. Implementing Quality of Service (QoS) policies is made possible via VLANs. Time-sensitive apps, like voice or video, are prioritized over less critical traffics, like file transfers. High-bandwidth applications can be isolated. VLANs provide a logical framework for managing network traffic, and this comes with simplicity. VLAN improves security and scalability while giving experts control over the network system. Despite the challenges of virtual machine migration, it provides a basis for efficient management in virtualized systems.

What is the Purpose of Creating VLANs in a Network Infrastructure?

Network infrastructure refers to the underlying framework of hardware and software resources that enable network connectivity, communication, operations, data exchange, and management within a system. It includes various components such as, physical devices, software components, network services and protocols.

A robust network infrastructure is essential for supporting business operations. Secure data sharing and communications are common and essential in businesses.

VLANs improve both safety and versatility while giving experts control over the network infrastructure. Despite the challenges of virtual machine migration, it provides a basis for efficient management in virtualized systems. A VLAN is a group of devices or network nodes that, although they are actually part of one or more LAN segments, communicate with one other as though they were a single LAN. In theory, a segment is usually utilized for a certain department and is isolated from the rest of the LAN by a bridge, router, or switch. When a station broadcasts packets, every other workstation in the VLAN receives them, but none outside of it. Many of the possible issues brought on by LANs, such as excessive network traffic and collisions, are made simpler by this. Data collisions and improper transmission occur when two workstations on a LAN connected by a hub submit data packets simultaneously. Because the collision spreads throughout the network, the LAN is busy, and users must wait until the collision has completely spread throughout the network before it can be used again, at which time the original data needs to be delivered again. By functioning as LAN groups, VLANs lower the frequency of collisions and the amount of network resources lost. A gateway or switch transfers data packets sent from a workstation in a segment. Segments contain collisions inside their boundaries. VLANs broadcast to all network devices without forwarding collisions. Because VLANs enable logical partitioning and enhanced data protection, they are more functional than even just being a partitioned LAN segment.

What Steps Are Involved in VLAN Implementation?

When planning VLANs for a network, there are several key considerations and best practices to keep in mind. First, the topology should be examined, the appropriate subdivision should be determined, and the purpose of the VLANs should be considered. It can be done by grouping the necessary devices together and isolating the traffic. Second, network performance and security should be considered. VLANs can improve network performance and security by reducing network congestion, limiting broadcast traffic, separating network traffic, and limiting access to specific network resources.

Crafting a robust VLAN setup tailored to your network's unique configuration and the array of network devices at play, like switches, routers, and access points, demands a nuanced approach. While the precise sequence of steps can vary according to your equipment and network architecture, there are some fundamental guidelines that often come into play when initiating a VLAN deployment:

• Determine the VLAN requirements by identifying the devices that need to be grouped together and the traffic that needs to be isolated.
• Use the appropriate commands to create VLANs on the switches or routers.
• Assign switch ports to the appropriate VLANs using the appropriate commands.
• Configure VLAN trunking, if necessary, to allow multiple VLANs to be carried over a single physical link.
• Configure VLAN tagging to identify which packets belong to which VLAN, if needed.
• Test and verify that the VLAN configuration is working as expected by testing connectivity between devices on different VLANs.

How can VLANs be effectively Secured?

Securing Virtual Local Area Networks is crucial to prevent unauthorized access and data breaches, mitigate potential security risks, and maintain the integrity of network traffic within each VLAN. VLAN hopping, MAC spoofing, ARP poisoning, and DHCP spying are just a few of the attacks that can compromise a VLAN. Bypassing VLAN limits and gaining access to private data, interfering with network operations, or starting new attacks are all possible through these attacks. VLANs can protect against illicit access or intervention by isolating distinct types of traffic, including data, voice, or management. Even if a setup manages broadcast traffic, it cannot be regarded as a secure "VLAN" if there are no genuine ACLs, firewall rules, or packet tagging to prevent unauthorized access by malware, internal attackers, and similar. With no regulations and minimal to nonexistent security between any of the network parts and systems, the network is essentially flat. VLAN security is critical for maintaining network confidentiality, availability, and integrity.

Best Practices for VLAN Security

Here are some strategies for segregating sensitive data and implementing secure VLAN management practices:

• Dynamic port security: One of the most effective ways to prevent spoofing is to use dynamic port security on the switch ports that are connected to end devices. Utilizing port security measures to limit the number of MAC addresses allowed on each switch port prevents unauthorized devices from connecting.

• ID, range, and access settings: Configuring VLAN ID and range settings can prevent VLAN hopping and spoofing attacks, and VLAN access control can be employed to restrict access. VLAN pruning is utilized to limit the number of VLANs that are allowed on a trunk.

• Unused Ports: Create a "Dead End" VLAN for unused ports by choosing any random number for the VLAN. Ensure that this VLAN is not configured with DHCP, Inter-VLAN routing, or device management functionality enabled. This enhances the security of the other VLANs. Assign the VLAN to any LAN port that is not currently being utilized.

• Monitoring and Auditing: Periodically audit the VLAN configurations to ensure that they align with the security policies. Verify that VLAN memberships are accurate and that there are no unnecessary ports in critical VLANs. Use network monitoring tools to analyze traffic within VLANs. Set up logging and alerts to detect suspicious or unauthorized activity.

• Data segregation: Place critical resources, such as servers and sensitive data, in separate VLANs to prevent unauthorized access and potential security breaches. VLANs are best kept as small and specific as possible. To reduce the possibility of unwanted access and compromise, creating unnecessarily large or all-encompassing VLANs should be avoided.

• Inter-VLAN Routing: VLANs are established to enable the segregation of network traffic, however, there are instances when it becomes necessary for VLANs to have the capability to route traffic amongst one other. Inter-VLAN routing is generally discouraged. If your firm need this, establish it with the highest level of security. When implementing inter-VLAN routing, it is important to use Access Control Lists (ACLs) to limit traffic access to servers that store sensitive or secret data.

  ACLs are used to regulate the flow of packets in a network by performing packet filtering. Packet filtering enhances security by imposing restrictions on incoming network traffic, controlling user and device access to a network, and preventing outbound data from exiting the network. IP access lists mitigate the risk of spoofing and denial-of-service attacks, while also enabling the temporary and dynamic granting of user access over a firewall.

• Access Control Lists (ACLs): ACLs on layer 3 switches or routers should be implemented to control traffic between VLANs. ACLs allow you to define rules that permit or deny traffic based on source and destination IP addresses, protocols, or ports. In addition, 802.1X authentication and VLAN hopping prevention can be implemented for port-based authentication to make sure that only authenticated devices can access the network. Disabling Dynamic Trunking Protocol (DTP) on switch ports that don't require trunking and using the "switchport no negotiate" command to prevent the negotiation of trunk links are some precautions for hopping prevention.

• Private VLANs and Network Access Control (NAC): Utilize PVLANs to provide further isolation within a VLAN. PVLANs divide a VLAN into sub-VLANs, allowing some devices to communicate while isolating others, and enhancing security in shared environments. Network access control solutions, on the other hand, enforce security policies before granting access to devices. NAC ensures that devices meet specific security requirements before they are allowed on the network.

• VoIP on VLANs: Voice traffic requires strict adherence to Quality of Service (QoS) requirements. In the scenario when your company's PCs and IP phones are connected to the same VLAN, both devices attempt to use the available bandwidth independently, without taking into account the presence of the other device. In order to prevent this conflict, it is advisable to use distinct VLANs for IP telephony voice traffic and data traffic.

Securing VLANs requires a holistic approach that encompasses both technical controls and security best practices. Awareness training, password policies, and the physical security of network equipment are the other important aspects of effective VLAN security. Network devices' firmware, operating systems, and software should be kept up-to-date with security patches. Unauthorized infrastructure access can be eliminated by implementing secure access policies and procedures. Another protection measure is securing the management interface by protecting the management interfaces of network devices, such as switches and routers, with strong authentication mechanisms such as SSH or HTTPS and access control lists to restrict access to authorized administrators. In a bad-case scenario, a backup and disaster recovery plan can save the day. Maintain regular backups of VLAN configurations and have a disaster recovery plan in place to quickly restore network functionality in case of security incidents.

What challenges and considerations arise with VLANs?

Implementing and managing VLANs offers multiple benefits and can be a powerful way to enhance network functionality, but it does come with its share of potential hurdles, complexities, and possible drawbacks. Managing and maintaining several VLANs can become complex and time-consuming as the network grows. VLAN configurations must be consistent and interoperable across all switches and routers, and VLAN performance and connectivity issues must be monitored and troubleshooted. There are security risks since attackers can use misconfigured ports or trunk lines to undertake VLAN hopping or denial-of-service attacks. To safeguard the VLANs, further security controls are required. If different vendors or versions of switches or non-standard devices and routers are utilized on the network, interoperability and compatibility problems could arise. You must guarantee that the switches and routers support the same VLAN tagging methods and capabilities so that devices may communicate with one another smoothly.

Successfully implementing and managing VLANs requires a combination of careful planning, thorough documentation, ongoing training, and a proactive approach to addressing challenges as they arise. Here are some common challenges and strategies to mitigate them for a successful VLAN deployment and operation:

• Misconfiguration: Incorrect VLAN configurations, such as assigning the wrong ports to VLANs, can lead to connectivity issues or security vulnerabilities. Implement strict change control procedures and document configurations thoroughly. Regularly audit configurations to ensure they align with network design.
• Scalability Concerns: As the network grows, managing an increasing number of VLANs can become complex and cumbersome. Implement hierarchical network designs with core, distribution, and access layers. Use VLAN naming conventions and documentation to keep track of VLANs efficiently.
• Inter-VLAN Routing: Enabling communication between VLANs while maintaining security can be tricky. Implement proper access control lists (ACLs) on routers or layer 3 switches to control traffic between VLANs. Consider using firewall appliances for more advanced traffic filtering.
• VLAN Overlap: VLAN IDs may overlap in different parts of the network, causing conflicts. Implement a standardized VLAN numbering scheme and document VLAN assignments carefully to avoid overlap. Use VLAN IDs consistently across devices.
• Troubleshooting Complexity: Diagnosing within or across VLANs might be challenging. Utilize network monitoring tools and diagnostic commands like ping, and traceroute for debugging. Training and documentation can help managers become proficient in troubleshooting VLAN-related problems.
• Device Compatibility: Not all network devices support VLANs or VLAN features uniformly. Before deploying VLANs, ensure that network devices (switches, routers, and access points) support the required VLAN features and standards. Plan for device upgrades or replacements if necessary.
• Resource and Change Management: Allocating appropriate resources (IP addresses, VLAN IDs, bandwidth) for each VLAN can be complex. Plan for resource allocation based on expected growth and usage patterns. Use IP address management (IPAM) tools to track and manage IP allocations. Frequent changes in VLAN configurations can introduce risks. Implement strict change management processes to review, test, and document all changes before implementation. Use staging environments for testing VLAN changes before deploying them in production.
• Training and Documentation: Network administrators may lack experience managing VLANs. Invest in training and certification programs for network staff. Encourage knowledge sharing and mentoring among team members to build expertise in VLAN management. Inadequate or outdated documentation can lead to confusion during network management. Maintain up-to-date documentation that includes VLAN IDs, names, IP subnets, and associated devices. Regularly review and update this documentation after the changes.

VLANs are a common security target, so it is important to design VLANs with security in mind. Their configuration and management involve maintaining and organizing all the data associated with your network, which is difficult when different devices save and store configurations in varying formats. Follow best practices for VLAN configuration and management to avoid potential issues. Design VLANs with security in mind, such as by configuring all the ports on all switches to be associated with them. Use VLAN monitoring and management software to maintain and organize all the data associated with your network.

One issue is Native VLAN mismatch, which happens when the interfaces of a switch are configured with different native VLANs, causing issues in the network. Configure the interfaces of a switch with the same native VLAN to avoid issues in the network. Another common issue is Inter-VLAN bridging, which is the concept of simultaneously bridging multiple VLANs together. Inter-VLAN bridging is sometimes needed to connect non-routable or unsupported routed protocols across several VLANs. Before configuring inter-VLAN bridging, various topology issues and restrictions must be dealt with. Avoid inter-VLAN bridging as much as possible. If it is necessary, address the topology considerations and limitations before configuring inter-VLAN bridging and consider using firewall appliances for more advanced traffic filtering.

What are VLAN Security Risks?

It is important to consider the following common VLAN security risks when planning a network that includes VLANs:

• The VLAN hopping approach involves delivering packets to a port that is often inaccessible from an end system in order to attack the network resources of the VLAN. Cybercriminals may establish a base of operations to attack other VLANs linked to the network by using VLAN hopping.
• In spoofing attacks, using a falsified VLAN tag can be employed in VLAN trunking to gain access to or interfere with traffic on other VLANs.
• CAM table overflow/MAC attacks make use of the fact that switches only keep track of the MAC addresses of the devices connected to their ports, making it impossible for switches to identify an attacker.
• Address Resolution Protocol (ARP) attack takes advantage of the ARP protocol to reroute traffic to a different device.

To mitigate these security risks, like VLAN hopping and spoofing attacks, best practices should be employed to keep the network secure. In the stages of planning, configuring, and deploying VLANs, VLAN access control, VLAN ID, and range settings should be used. The traffic flow should be monitored to restrict access to VLANs and prevent unauthorized access, and VLAN pruning can help limit the number of VLANs that are allowed on a trunk. Given the fact that there are different VLAN configurations that can be used depending on the specific network requirements, such as access mode, trunk mode, and hybrid mode, when setting up VLANs, it is important to configure access ports correctly and set up VLANs with department-based segmentation.

How does Inter-VLAN Routing Facilitate Communication?

Inter-VLAN routing is the process of forwarding network traffic from one VLAN to another VLAN to enable communication between different VLANs. By default, devices within the same VLAN can communicate with each other, but they cannot directly communicate with devices in other VLANs. Layer 3 devices, such as routers and Layer 3 switches, contribute to inter-VLAN routing functionality. These devices have the capability to operate at the network layer (Layer 3) of the OSI model, making them capable of routing traffic between different IP subnets or VLANs. Inter-VLAN Routing offers logical network segmentation, enhanced flow of network traffic, flexibility, and consolidated routing. Centralized Layer 3 devices can handle routing for multiple VLANs, streamlining network administration and allowing users to tailor their network architecture to their specific needs. It increases efficiency by reducing broadcast domains and allowing for more precise control over routing decisions.

Here is the role of Layer 3 devices in Inter-VLAN Routing and some ways in which they enable inter-VLAN routing and provide faster routing performance:

• Switch Virtual Interfaces (SVIs): Layer 3 switches use SVIs to route traffic between VLANs. An SVI is a virtual interface that represents a VLAN and has an IP address associated with it. When a Layer 3 switch receives a packet from one VLAN destined for another VLAN, it forwards the packet to the appropriate SVI, which then routes the packet to the destination VLAN.
• Hardware-based switching: Layer 3 switches use hardware-based switching to achieve higher packet processing rates than routers. This means that Layer 3 switches can perform the routing process quickly, without the need for software-based routing.
• Scalability: Layer 3 switches are more scalable than router-on-a-stick solutions, which transport traffic between VLANs using a single physical interface. They are deployed in significant company networks to enable inter-VLAN routing since they can handle a greater number of VLANs while giving better routing functionality.
• Subnet Assignment: Each VLAN is typically associated with a specific IP subnet. For example, VLAN 10 might use the IP subnet 192.168.10.0/24, while VLAN 20 might use 192.168.20.0/24. Layer 3 devices assign IP addresses to the VLAN interfaces corresponding to these subnets.
• Routing Tables: Layer 3 devices maintain routing tables that specify how to forward traffic between different IP subnets. These tables contain entries that define the next-hop IP address or interface for each destination subnet.
• VLAN Interfaces: To enable inter-VLAN routing, Layer 3 devices create virtual interfaces (SVIs - Switched Virtual Interfaces) corresponding to each VLAN. These SVIs serve as the gateway for devices in their respective VLANs.
• Packet Forwarding: When a device in one VLAN wants to communicate with a device in another VLAN, it sends its traffic to its VLAN's SVI (gateway). The Layer 3 device then performs the following steps:
  • Receives the packet from the source VLAN and determines the destination IP address.
  • Consults its routing table to find the appropriate path to the destination IP subnet.
  • Forwards the packet to the destination VLAN by rewriting the Ethernet frame header with the appropriate MAC address of the next-hop device or interface.
  • The packet is then received by the destination VLAN's SVI, and it can deliver the packet to the destination device within that VLAN.
• Return Traffic: When the destination device in the second VLAN responds to the packet, its traffic follows a similar process in reverse, effectively enabling two way communication between the VLANs.

What is the Difference Between VLAN and Subnet?

Virtual Local Area Networks and Subnets constitute significant networking concepts, but they perform different functions. VLANs are the ideal path to choose when you need to divide networks digitally rather than physically. They are more adaptable than subnets because they allow you to organize devices according to function, location, or any other criteria you pick. Due to the fact that VLANs do not require additional hardware, they are easier to administer and less expensive than subnets. The following are the fundamental distinctions between VLANs and subnets:

VLAN stands for Virtual Local Area Network and is defined by the 802.1q protocol. They allow us to virtually separate our LANs into smaller networks, which work like normal LANs except they are logically or virtually separated as opposed to physically. They provide all of the benefits of physically separating our network virtually without spending extra money on hardware. VLANs are a layer 2 construct, meaning they operate at the data link layer of the OSI model, and they separate networks virtually.

On the other hand, subnetting divides broadcast domains, which improves speed, efficiency, and network performance. They are a way of breaking up a larger network into smaller, more scalable, and more secure networks. Subnets are a layer 3 construct, meaning they operate at the network layer of the OSI model and separate networks physically.

VLANs and subnets are both used to segment traffic, enhance performance, and improve the security of a network, while one VLAN operates logically and the subnet physically.

What is the Difference Between VLAN and LAN?

LAN and VLAN are two different types of networks that serve different purposes. Here are the key differences between LAN and VLAN:

LAN stands for Local Area Network and it is a group of network devices that allow communication between connected devices. They are used to connect a group of devices, such as computers and printers, to a server via cables. LANs work on a single broadcast domain, and they are limited to a particular geographic area.

On the other hand, VLAN stands for Virtual Local Area Network and it allows multiple LANs and associated devices to communicate via wireless internet. VLANs are used to enhance the performance of LANs and they work on multiple broadcast domains. They are a virtualized connection thaLANs,t connects multiple devices and network nodes from different LANs into one logical network.

What are the differences between VLAN and WLAN?

Virtual Local Area Network (VLAN) is a logical subnetwork that segments a larger physical network into smaller, isolated networks. This allows devices on the same physical network to communicate as if they were on separate networks. The main goal is better security and efficiency.

Wireless Local Area Network (WLAN) is a type of local area network that uses wireless communication methods, such as radio waves, to connect devices. This enables mobility and flexibility for users within the coverage area of the wireless access points. A summary of key differences between VLAN and WLAN can be found in the following table.

Feature	VLAN	WLAN
Definition	Logical segmentation of a physical network into smaller networks.	Wireless networking technology that connects devices without cables.
Functionality	Segmentation & Isolation. Creates separate broadcast domains within a LAN for better traffic management and security.	Wireless connectivity. Facilitates wireless communication between devices in a local area.
Implementation	Network switches, software. Implemented using managed switches and requires configuration for segmentation.	Utilizes wireless access points (WAPs) to transmit data via radio waves.
Flexibility	Allows dynamic reconfiguration of network segments without physical changes.	Supports multiple SSIDs for different user groups or purposes within the same physical area.
Protocols Used	Typically uses Ethernet protocols with VLAN tagging for data packets.	Follows IEEE 802.11 standards for wireless communication.
Cost	Generally lower cost due to reduced cabling needs but may require more complex setup.	May involve higher costs due to the need for wireless infrastructure (e.g., access points).
Use Cases	Commonly used in enterprise environments to manage user groups, departments, or services efficiently.	Widely used in homes, offices, and public spaces for mobile device connectivity.

Table 1. Key differences between VLAN and WLAN

What Tools and Solutions Aid VLAN Management?

There are several tools and software available for efficient VLAN administration and monitoring. Some VLAN management tools that can be employed on the market are as follows:

1. SolarWinds Network Configuration Manager: SolarWinds Network Configuration Manager allows you to automate key operations, apply device configuration changes in bulk, and view the status of a range of devices at a glance. It ensures all the configurations are non-conflicting and appropriate. You can receive alerts when changes are made to your VLAN and use real-time monitoring to catch potential issues in your virtual network. The software offers network security safeguards, such as detecting security misconfigurations and failed switches, replacing switch outages, and automatically backing up VLAN configuration files for disaster recovery. It can also provide automated notifications, detailed reports when network configuration files change, and scheduled reports to update you on issues and trends. It can also integrate with other SolarWinds network management tools.
2. ManageEngine OpManager: ManageEngine OpManager includes a VLAN discovery tool that detects new VLANs and assists you in doing effective VLAN monitoring. It enables you to automate VLAN updates, receive alerts when your VLAN is changed, and use real-time monitoring of VLAN performance, bandwidth utilization, and traffic to detect potential issues in your virtual network. Maintenance is more effective when users are connected to smaller teams. It also provides VLAN provisioning and management across diverse network infrastructures and integration with other ManageEngine products for comprehensive network management.
3. WhatsUp Gold: WhatsUp Gold offers comprehensive VLAN management capabilities. It has a flexible SNMP-based interface that allows automatic deployment of VLANs across multiple devices and ports. Tasks like backup and restoring configuration files, building configuration templates, adding and copying VLANs from one device to another, and setting up and receiving notifications and alerts are all made simple with the comprehensive, single-interface solution. It also offers functionality across a wide vendor spectrum.
4. Cisco Network Assistant
5. VLAN Management Software (VMS)
6. PRTG Network Monitor
7. Infoblox NetMRI

What are the Benefits of Using VLAN Management Tools?

Efficient VLAN administration and monitoring tools and software play a critical role in simplifying the management of complex network environments. They streamline VLAN provisioning, configuration, and monitoring tasks, helping network administrators save time, reduce errors, and improve network performance. Employing VLAN administration and monitoring tools can automate key operations, apply device configuration changes in bulk, view the status of a range of devices at a glance, and ensure all the configurations are non-conflicting and appropriate. These tools can help you troubleshoot more effectively and receive automated notifications when network configuration files change.

Some of the advantages of employing these tools to automate VLAN provisioning and management tasks:

• Automating VLAN provisioning and configuration activities reduces manual work and the possibility of human error.
• VLAN settings are uniform across the network thanks to templates and defined setups, which improve reliability.
• Monitoring and reporting in real-time provide insight into VLAN performance, traffic patterns, and potential issues.
• Automation features that enable scheduled backups, alarms, and auto-remediation of VLAN-related issues
• Efficient management solutions can more effectively enforce security regulations, control access, and detect unwanted VLAN activities.
• Expanding with networks as they grow, making it easier to handle larger and more complicated VLAN setups.
• Tools such as Infoblox NetMRI can help ensure that VLAN configurations meet regulatory compliance criteria.
• VLAN documentation is essential for troubleshooting and auditing, and these tools can help keep accurate records.

What is VLAN 1?

VLAN 1 is a special VLAN that serves as the default VLAN for many network devices, particularly those compliant with the IEEE 802.1Q standard. It is automatically assigned to all switch ports upon initial configuration. It is a fundamental aspect of network management. VLAN 1 is primarily used to carry control and management traffic, such as Spanning Tree Protocol (STP) and Simple Network Management Protocol (SNMP) messages. Importantly, VLAN 1 cannot be deleted or renamed. This establishes its presence across all compatible devices.

While VLAN 1 often acts as the default VLAN, the terms are not synonymous. The default VLAN refers to the initial VLAN configuration for switch ports when they are factory reset. For many devices, this default setting is indeed VLAN 1, but administrators have the option to change this to enhance security by isolating devices from the default settings.

VLAN 1 cannot be deleted or renamed. It carries essential control traffic. Default VLAN can be reconfigured by network administrators. It may differ from VLAN 1 depending on security policies. This distinction is crucial for network design and security. Employing VLAN 1 without modifications can expose the network to vulnerabilities like unauthorized access and VLAN hopping attacks. Despite its utility, many network professionals recommend avoiding the use of VLAN 1 for sensitive management tasks due to its inherent security risks. Instead, creating a separate management VLAN can be more secure through commonly known defaults. VLAN 1 is typically utilized in several key areas.

• VLAN1 carries critical management protocols necessary for network operations. This includes control traffic like VLAN Trunking Protocol (VTP), Spanning Tree Protocol (STP), and Cisco Discovery Protocol (CDP).
• When switches are first set up, all ports are part of VLAN 1. The aim is immediate communication without additional configuration.
• VLAN 1 serves as the native VLAN on trunk links by default. This means it handles untagged traffic between switches unless explicitly configured otherwise. It means they lack the 802.1Q tag that identifies the VLAN.
• VLAN 1 is often used in smaller or legacy networks where the administrative overhead of reassigning VLANs is not required.
• It is commonly utilized during the initial setup of switches and basic connectivity tests.
• In environments where no advanced VLAN segmentation is required, VLAN 1 may remain as the operational VLAN.
• Some layer 2 control traffic, like Bridge Protocol Data Units (BPDU ), runs on VLAN 1 unless explicitly configured otherwise.
• VLAN 1 can be utilized for inter-VLAN routing, although this practice is generally discouraged due to security concerns.

What is Trunk VLAN?

A network configuration that efficiently moves data between multiple companies without the need for one-to-one links is sometimes referred to as a trunk. It functions similarly to a steady network of tree trunks, with each trunk distributing water to every branch and leaf. These trunks in a network distribute many signal streams to the devices connected to the network and their proper destinations. Numerous subnets that swap traffic between ports are frequently seen in networks. Congestion may occur and cause issues for the network as a result of the switches' speed and port limits. Because VLAN trunking enables more efficient network access between two nodes by transporting several signals simultaneously, it aids in the management of data and traffic on a network with more connectivity paths. It is used in the telecom sector to construct multiple-signal lines and connect switching centers.

VLAN trunking allows a VLAN to be extended throughout the network. Trunk links are required when implementing several VLANs throughout a network in order to maintain the proper segregation of VLAN signals so that each can reach its destination. Because numerous VLANs may be set up on a single port, this is more efficient. This system must be able to differentiate and route signals. In order to identify frames as they move between switches, a trunking VLAN port always requires identification tags. The Ethernet frame is tagged as it travels through by IEEE 802.1Q. It is the most used protocol for trunking, and it designates it as a member of a particular VLAN. Ultimately, this tag, which contains the Media Access Control (MAC) address, assists in directing the Ethernet frame as it travels across the host port and the trunked link to the appropriate endpoint. Trunk VLANs are utilized in various networking scenarios.

• Trunks are essential for linking multiple switches together while allowing them to share the same set of VLANs without needing separate physical connections for each. Connecting switches to routers to allow routing between VLANs.

• In data centers or server farms, trunking supports virtual machines on different hosts to communicate over the same network infrastructure while remaining logically separated by their respective VLANs.

• Trunks simplify network architecture by reducing the number of physical links required. Scalable network designs are possible now.

• In environments where different clients or departments require isolated networks, trunking enables the efficient use of resources and data flow.

What is the Difference Between Trunk VLAN and Default VLAN?

The differences between a trunk VLAN and a default VLAN is as follows.

Feature	Trunk VLAN	Default VLAN
Purpose	Uses a single connection to transport traffic for several VLANs. Facilitates inter-VLAN communication	Assigned to ports on a switch with no explicit VLAN configuration. Default by nature. Management and control traffic unless explicitly changed.
Tagging	Frames are tagged with VLAN IDs. Switches identify which VLAN the traffic belongs to.	Frames are typically untagged unless configured.
Connectivity	Connects switches or other devices that need to support multiple VLANs	Primarily used for devices on the same VLAN

Table 2. The differences between a trunk VLAN and a default VLAN

What is VLAN ID?

A Virtual Local Area Network Identifier (VLAN ID) is a unique numerical value assigned to a VLAN. It is used to identify and manage different virtual networks within a physical network. The VLAN ID is embedded in the Ethernet frame header as part of the VLAN tag. This tagging allows switches to determine which VLAN the frame belongs to and how to forward it appropriately. Without VLAN IDs, devices within the same physical network would be unable to effectively segment their traffic. Each VLAN ID is a 12-bit value, which means up to 4,096 unique VLANs within a single switching domain. It is defined by the IEEE 802.1Q standard and is a crucial element for tagging Ethernet frames with VLAN information. The range of VLAN IDs are as follows;

• 0 and 4095: Reserved VLANs.
• 1: Default VLAN on most switches.
• 2 to 1001: Standard VLAN range (configurable on most switches).
• 1002 to 1005: Reserved for legacy technologies like FDDI and Token Ring.
• 1006 to 4094: Extended VLAN range (used in modern networking).

How is VLAN ID Used?

VLAN IDs are employed in many cases in networking. It is mainly utilized in VLAN Tagging and VLAN configuration. They are needed when creating distinct broadcast domains within a physical network. Sometimes a device transmits a frame on a trunk link and this link can carry multiple VLANs. In this scenario, the VLAN ID is inserted into the frame's header. The aim is to identify the VLAN to which the frame belongs. Admins configure switches and other network devices to clarify which ports belong to which VLANs and direct them accordingly.

While VLANs isolate traffic, there are scenarios where communication between different VLANs is necessary. This is achieved through routers or Layer 3 switches that can route traffic between VLANs. The VLAN ID plays a critical role here to apply correct routing policies based on the originating VLAN of the traffic. Without proper segmentation with the usage of VLAN IDs, sensitive data could be exposed to unauthorized users. For example, if all devices operate on a default VLAN, which is often VLAN 1, it creates a broad broadcast domain that attackers can exploit. VLAN IDs map virtual machines (VMs) or containers to specific VLANs in cloud or data center networks, and they map wireless SSIDs to VLANs. VLAN IDs allow trunk links to carry traffic for multiple VLANs between switches or other network devices.

Without clear VLAN segmentation, identifying issues within the network becomes challenging. Misconfigured devices may inadvertently communicate with each other. Attackers can exploit vulnerabilities in VLAN configurations such as double tagging to access other VLANs in a compromised environment. In larger networks, the absence of VLAN IDs can create administrative chaos and limit the network's scalability. Voice, video, and data traffic might conflict without VLAN-based separation. This results in a reduction of the quality of service (QoS).

What is Default VLAN?

A Default VLAN is the initial VLAN configuration that all switch ports belong to when a network switch is first powered on or reset. Typically, this is VLAN 1 on many switches. The Default VLAN serves as a catch-all for any ports that have not been explicitly assigned to other VLANs. This means that any device connected to a switch port can communicate with other devices on the same switch that is also part of the Default VLAN. It facilitates basic connectivity inside the network.

The term Default VLAN reflects its role as the pre-configured VLAN that all ports belong to by default. In many switches, particularly Cisco devices, the Default VLAN is fixed as VLAN 1 and cannot be deleted or renamed. Other VLANs may be specifically assigned for certain purposes, like data or management. The Default VLAN encompasses all unassigned ports. If not handled appropriately, this may result in security flaws.

There are two different types of default VLANs. The VLAN to which all of a device's ports belong when it is turned on is commonly referred to as the default VLAN. VLAN 1 is the default on the majority of switches, and it ought to be modified for safety concerns. A VLAN that determines which all ports are allocated when not in use is referred to as the "default VLAN" by some network management.

The Default VLAN is primarily used in initial network setup, troubleshooting, and basic connectivity. On many devices, the default VLAN handles traffic for management protocols like Telnet, SSH, and SNMP. It simplifies the initial configuration and management process. Devices find the chance to connect without requiring immediate VLAN assignments. For network executives, the default VLAN reduces complexity. By default, broadcast traffic like ARP requests is transmitted within the default VLAN if no segmentation is configured. Default VLAN provides interoperability with systems or legacy devices that require a VLAN configuration by default. In cases where network issues arise, having a Default VLAN can help isolate problems since all unconfigured ports will still communicate within this VLAN. It enables devices to communicate within a single broadcast domain. It is useful for small networks or during initial deployment phases.

What is a Native VLAN?

A Native VLAN is a specific VLAN designated to carry untagged traffic on a trunk port in a network. When a switch receives untagged frames on a trunk link, it automatically assigns these frames to the native VLAN. This concept is primarily defined by the IEEE 802.1Q standard, which governs VLAN tagging in Ethernet networks. The native VLAN comes handy for devices that do not support VLAN tagging. It enables your VLAN to accommodate legacy devices or devices that do not tag their traffic, such as network-attached devices and certain wireless access points. Untagged traffic can still be processed inside the network architecture. It is possible to configure the Default VLAN and Native VLAN to the same VLAN ID in certain situations. Nonetheless, using distinct VLAN IDs is frequently advised for improved community management and security.

What is the Difference Between Native VLAN and Default VLAN?

The differences between a default VLAN and a native VLAN can be seen in the following table.

Feature	Default VLAN	Native VLAN
Scope	Applies to all ports on a switch	Applies specifically to trunk ports
Tagging	All traffic is untagged	Only traffic belonging to this VLAN is untagged
Purpose	Initial connectivity and legacy device support. Initial configuration for all switch ports.	Primarily for trunk link communication. Handles untagged traffic on trunk ports.
Security Risk	Widespread access if default settings are not changed.	Potential for VLAN hopping if misconfigured.
Encapsulation	It supports .1Q and ISL.	Only supports .1Q.
VLANs per Switch	One default VLAN per switch.	There can be numerous native VLANs as there are .1Q trunks on the switch.

Table 3. The differences between a default VLAN and a native VLAN

What Role Does VLAN Tagging Play in Ethernet Frames?

Ethernet frames are the fundamental units of data used in Ethernet networks. They encapsulate data for transmission across local area networks (LANs). An Ethernet frame consists of several fields that facilitate communication between devices on a network.

VLAN tagging is a method used to identify and manage traffic from different Virtual Local Area Networks (VLANs) within a single physical network infrastructure. This technique is standardized by the IEEE 802.1Q protocol, which defines how VLAN tags are added to Ethernet frames. When VLAN tagging is implemented, each Ethernet frame receives an additional header that includes;

• Tag Protocol Identifier (TPID): A 16-bit field indicating that the frame is VLAN-tagged (value 0x8100 for 802.1Q).
• Priority Code Point (PCP): A field that can be used for Quality of Service (QoS) prioritization purposes. It indicates the priority level of the frame with a 3-bit field.
• Drop Eligible Indicator (DEI): A 1-bit field to indicate frames that can be dropped during congestion.
• VLAN Identifier (VID): A unique identifier for each VLAN, allowing switches to segregate traffic appropriately. A 12-bit field specifying the VLAN ID (0-4095).

VLAN tagging plays a critical role in enhancing Ethernet frames by enabling efficient traffic management across multiple VLANs. Some key functions of VLAN tagging are as follows.

• VLAN Identification: VLAN tagging ensures that Ethernet frames are associated with the correct VLAN. This enables devices to distinguish between traffic belonging to different VLANs on the same physical network.
• Inter-Switch Communication: Ethernet frames can traverse trunk links which carry multiple VLANs). VLAN tags come handy to segregate the traffic and keep data integrity.
• Segmentation and Security: Prevents frames from being inadvertently delivered to devices on other VLANs.
• Multi-Tenant Environments: Enables network virtualization even when using shared infrastructure. Does this by logically isolating traffic for different tenants.
• Quality of Service (QoS): The priority field within the VLAN tag lets prioritize critical traffic. Performance is better for latency-sensitive applications.
• Inter-VLAN Routing Support: VLAN tagging is crucial for inter-VLAN communication, as Layer 3 devices (routers or Layer 3 switches) use the tags to route traffic appropriately.

Why is VLAN Tagging Important for Ethernet Frames?

A switch uses variables, particularly the VLAN ID, to decide how to forward an Ethernet packet with a VLAN tag inside the network. Despite possibly passing over the same physical network infrastructure, network traffic is successfully segregated by treating frames with different IDs as belonging to distinct VLANs. The Priority Code Point (PCP) field in the VLAN tag allows administrators to assign priority levels to Ethernet frames. Critical traffic, such as voice or video, can be given higher priority to ensure better performance and reduced latency. Ethernet frames with VLAN tags can traverse trunk links, which carry traffic for multiple VLANs. The VLAN tag allows switches and routers to correctly forward the frame to its designated VLAN. VLAN tagging is helpful, particularly in larger networking systems where administrators must concurrently manage several department divisions and goals, equipment and client kinds, network types, authorizations, and other considerations. Additionally, it assists network administrators of all sizes in becoming more organized, comprehending the traffic that passes through their network, and logically segmenting the network to enhance both traffic flow and performance. Particularly via VLAN tagging, customers can select from a variety of approaches and protocols, including IEEE 802.1Q and ISL.

How Does VLAN Help in Reducing Broadcast Domains in a Network?

A broadcast domain is a logical segment of a network in which all devices can receive broadcast messages sent by any other device within that domain. In simpler terms, when a device sends a broadcast message, every device in the same broadcast domain receives it. Broadcasts are commonly used for essential network services like Address Resolution Protocol (ARP) and Dynamic Host Configuration Protocol (DHCP). They need to discover each other without knowing their specific addresses. In traditional Ethernet networks, all devices connected to a hub or a switch belong to the same broadcast domain.

Small size of broadcast domains is preferred for network performance, security, and manageability. Large broadcast domains can lead to network congestion as each broadcast message is sent to all devices. It is consumption of bandwidth and processing power and can slow down the network. Smaller broadcast domains limit the exposure of devices to unnecessary traffic and potential security threats, such as malware that spreads through broadcasts. Smaller domains simplify network management by allowing administrators to isolate problems and manage traffic more effectively.

Devices can be grouped into VLANs based on function or department rather than physical location. This is better resource management and reduced broadcast traffic. Switches can be configured to assign specific ports to particular VLANs, further controlling the flow of broadcast traffic. Trunk ports can carry traffic from multiple VLANs. VLAN tagging (via IEEE 802.1Q) enables switches to carry traffic from multiple VLANs over a single trunk link while keeping the VLANs logically separated. This ensures broadcast traffic is restricted to the originating VLAN. VLANs manage traffic flow more efficiently by limiting broadcasts to only those devices that need to receive them. With smaller broadcast domains, there is less clutter on the network.

How can Zenarmor NGFW protect VLANs?

Zenarmor Next-Generation Firewall (NGFW) is a firewall that can be deployed practically anywhere. Zenarmor NGFWs appliance-free, all-in-one, all-software, lightweight, and simple architecture makes it simple to deploy on any platform with a network connection, including the cloud. It is a plugin for the OPNsense firewall that offers cutting-edge, modern features. For features like application control, network analytics, and TLS inspection purposes, Zenarmor NGFW is a suitable application, which can run on all open-source firewalls.

You may easily protect your VLANs against cyber threats by selecting VLAN interfaces individually on the policy configuration page of Zenarmor. As a best practice, it is advised to select the physical interface or parent interface of VLANs that you want to safeguard.

How can VLANs be configured on OPNsense?

OPNsense is an open-source firewall and routing software based on FreeBSD. It is a strong network firewall solution that includes VLAN capabilities. It improves network efficiency and offers a strong defense against potential attacks by making it simple for network managers to establish, monitor, and secure VLANs. It has guest access, IDS/IPS, WireGuard VPN, content filtering, DNS level filtering, and built-in scanners.

You can easily create and configure a VLAN interface on your OPNsense node by following the next steps to get VLAN benefits such as increased security, traffic control, and network scalability:

1. Prepare the Network Environment
   1. Examine the hardware and topology of your network.
   2. Determine which network switches, routers and other components will be included in your design.
   3. Determine a VLAN's strategic location and comprehend the physical setup.
   4. Select separate interfaces for your LAN (internal) and WAN (external) connections. For each interface, use separate physical network ports or adapters.
2. Create VLANs in OPNsense
   1. Access the OPNsense Web User Interface
   2. Navigate to Interfaces > Other Types > VLAN
   3. Add a New VLAN
   4. Select the Parent Interface and Configure VLAN Tagging
   5. Assign Logical Interfaces to the VLAN
3. Configure VLAN Interfaces
   1. Access the VLAN Interface Settings
   2. Enable the VLAN Interface
   3. Name the VLAN Interface
   4. Set Up a Static IPv4 Address for the VLAN
   5. Configure DHCP for Automatic IP Address Assignment
4. Configure Firewall Rules for VLANs
   1. Create new rules to facilitate desired traffic flow across and within VLANs.
   2. Adjust the rules to match the specific needs of each VLAN.
   3. To react to changing network needs, review and change firewall rules on a regular basis.
5. Test the VLAN Configuration

How are VLANs Configured on pfSense?

pfSense software is a FreeBSD-based firewall/router software distribution. To create a dedicated firewall/router for a network, the open-source pfSense Community Edition (CE) and pfSense Plus are installed on a physical computer or a virtual machine. It is configured and upgraded via a web-based interface and does not require knowledge of the underlying FreeBSD system to manage. pfSense has extensive capabilities, including firewall, VPN, and router capabilities in a single package. It is incredibly flexible and scalable, with capabilities such as GeoIP blocking, anti-spoofing, dynamic DNS, and simultaneous IPv4 and IPv6 compatibility.

To configure VLANs in pfSense, there are two methods, including console VLAN configuration and web interface VLAN configuration.

For VLAN configuration on pfSense Web User Interface, you may follow the next steps:

1. Go to Interfaces > Assignments.
2. Select VLANs, then click "Add" to add a new pfSense VLAN in the Assignments section.
3. Select the interface that will be the VLAN parent interface in the Parent Interface drop-down menu.
4. Select the VLAN ID, in the VLAN Tag drop-down menu.
5. "Save" to create the VLAN.
6. Select the new VLAN and click "Add" to add and enable the interface in the Available Network Ports menu.
7. Select the unique name that is automatically assigned to the interface.
8. Configure the interface as preferred.

After configuring the VLANs, you must use them with your switch or access point.