What is Virtual Local Area Network (VLAN) / 802.1.q ?

In the world of computer networking, achieving optimal resource utilization, network scalability, effective network management and security is key. A common approach to attaining these objectives is utilizing virtualization.

By utilizing virtualization we can connect a selected group of end devices in the same physical network to one VLAN instance. Each VLAN instance is an isolated switching domain and there can be multiple VLAN instances present at the same time. The isolation of VLANs provides better network scalability and troubleshooting, prevents data leaks, isolates network disruptions and enables access control resulting in increased security and improved network management.

VLANs efficiently manage network resources like bandwidth and hardware allocation. By designating specific VLANs for different departments or purposes, network administrators ensure that resources are allocated precisely where needed. This prevents wastage of bandwidth on non-critical tasks and optimizes resource usage according to each VLAN’s demands.

As businesses and networks expand, scalability becomes crucial. VLANs offer a scalable solution without the need for excessive physical hardware and infrastructure expansion. Logical segmentation of the network allows for accommodating more devices and subnetworks while maintaining manageability, reducing costs, and streamlining the growth process.

Managing complex networks can be challenging, especially in large setups. VLANs simplify network management by organizing devices logically based on their function or location. This logical grouping enhances management and monitoring capabilities, enabling administrators to apply policies, controls, and monitoring tools to each VLAN for efficient network management and troubleshooting.

In addition, VLANs play a vital role in improving network security. By creating isolated VLAN instances within the network, the risk of unauthorized access and data breaches is reduced. By offering granular control over resource access, sensitive data can be isolated with strict access controls. As a result, this segmentation makes it significantly more challenging to compromise the entire network.

In summary, VLANs are a valuable tool for addressing network challenges related to resource utilization, scalability, management, and security. By implementing VLANs, organizations can ensure that their networks are efficient, adaptable, well-organized, and secure.

VLAN in StoneWork

StoneWork is a routing platform that supports VLAN and can be used as a virtual multi-tenant router. StoneWork redirects traffic per customer to separate subinterfaces (VLAN 2 and VLAN 3). Each subinterface is connected to new VRF (Virtual Routing and Forwarding) table dedicated to that customer. The customer interface and VLAN in StoneWork are in the same IP subnet. It is because the path between them is connected through Bridge domain. That means that forwarding of packets is handled purely by the L2 layer. What goes into VLAN 2 goes out to customer1. What goes into VLAN 3 goes out to customer 2. 

You can find VLAN configuration examples in StoneWork on our github here.


If you are looking for an all-in-one routing platform with VLAN support, contact us.

IEEE 802.1Q

IEEE 802.1Q, or simply VLAN tagging, is a networking standard for implementing Virtual LANs (VLANs) on Ethernet networks. 802.1Q introduces a method for adding VLAN identification information to Ethernet frames. This allows network administrators to logically segment a single physical Ethernet network into multiple virtual LANs, each with its own unique VLAN identifier (VLAN ID).

Key characteristics of the IEEE 802.1Q standard

VLAN Tag Structure: At the heart of IEEE 802.1Q is the VLAN tag structure. The tag is a 32-bit field inserted into the Ethernet frame’s header. This tag contains essential information that facilitates the proper routing of frames within the VLAN infrastructure.

VLAN ID: The most critical component of the VLAN tag is the VLAN Identifier (VLAN ID), a 12-bit field. The VLAN ID is used to identify the specific VLAN to which the frame belongs. This identifier ranges from 1 to 4095, with some IDs reserved for specific purposes.

Priority and Drop Eligibility: The VLAN tag also includes fields for priority (3 bits) and drop eligibility (1 bit). These fields determine the priority of the frame’s transmission and whether it should be given priority treatment over other frames.

VLAN Tagging: When a switch receives an Ethernet frame that needs to be transmitted across a trunk link or to a device in a different VLAN, it adds the appropriate VLAN tag to the frame’s header. This tag encapsulates the frame with the necessary VLAN information.

Trunking and Frame Forwarding: Trunking, enabled by IEEE 802.1Q, allows switches to transmit frames from multiple VLANs over a single physical link. Each frame is tagged before transmission. On the receiving end, switches extract the VLAN tag, allowing them to direct the frame to the appropriate VLAN or perform inter-VLAN routing.

Interoperability: One of the strengths of IEEE 802.1Q is its standardization, which ensures compatibility between networking equipment from different manufacturers. This allows for seamless integration of switches and routers that support the protocol.

Q-in-Q (Double Tagging): To further enhance network segmentation, IEEE 802.1Q introduced Q-in-Q or double tagging. This technique involves adding an additional 802.1Q tag to an already tagged frame. This is useful for service providers or large enterprises that need to maintain VLAN segregation even when frames traverse multiple networks.

In conclusion, IEEE 802.1Q is a foundational protocol that enables the effective implementation of VLANs. By facilitating VLAN tagging and trunking, IEEE 802.1Q empowers network administrators to create flexible, efficient, and secure networks.

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