Why VLANs still matter is a top I have been wanting to cover for some time.
As a network architect, I’ve witnessed countless shifts in technology. We’ve seen the rise of Software-Defined Networking, the promise of true microsegmentation, and the pervasive move to cloud everything.
Some newer engineers, captivated by the latest buzzwords, might even whisper that the humble VLAN, the workhorse of network segmentation for decades, is becoming obsolete.
Let me assure you, from my vantage point of years designing and troubleshooting complex infrastructures, that couldn’t be further from the truth.
VLANs aren’t going anywhere. In fact, they remain a profoundly important and foundational element in nearly every network I touch.
At its heart, a VLAN, or Virtual Local Area Network, is a logical grouping of devices that can communicate as if they were on the same physical wire, regardless of their actual physical location. It achieves this by creating separate broadcast domains within a single physical switch or across multiple switches.
In simpler terms, imagine taking a large, open-plan office floor and, without building new walls, logically dividing it into smaller, sound-proofed rooms. Each room gets its own conversation space, isolated from the others. This core ability to segment has always been, and continues to be, critically important.
More Than Just Basic Segmentation
The initial brilliance of VLANs was their ability to reduce broadcast traffic and improve network performance by shrinking broadcast domains.
In a large, flat network, every device sees every broadcast, leading to unnecessary overhead and potential congestion. VLANs put a stop to that. They contain broadcast storms, which, let me tell you, can still bring down a network faster than you can say “Spanning Tree Protocol.”
This traffic management alone is reason enough for their continued existence. They also make it far simpler to apply Quality of Service (QoS) policies, allowing us to prioritize critical traffic like Voice over IP or video conferencing by assigning it to a dedicated VLAN.
Beyond performance, the security aspect of VLANs is often underestimated. Especially by those looking for a flashier solution. VLANs provide essential logical isolation. We use them to separate sensitive departments like finance or HR from the general user population, or to create completely isolated guest networks.
Should a security incident occur on one VLAN, its blast radius is immediately contained, preventing rapid lateral movement across the entire network.
Many regulatory and compliance frameworks, like PCI DSS for handling credit card data, explicitly or implicitly require this type of logical separation. So, VLANs are a non-negotiable component of our compliance strategy.
Flexibility, Scalability, and the Integration with Modern Tech
From a design and operational perspective, VLANs offer incredible flexibility and scalability. They allow us to group users or devices based on function, department, or application, irrespective of where they are physically plugged into the network.
This makes moves, adds, and changes (MACs) significantly easier. If an engineer moves from one floor to another, we don’t have to re-IP their machine or reconfigure a complex access list . We simply ensure their port is assigned to the correct VLAN, and their network access follows them.
This logical grouping also allows for more efficient use of IP address space. Achieved by enabling us to carve out smaller subnets tailored to the needs of each segmented group.
Crucially, VLANs are not being replaced by newer technologies. They often serve as the vital underlying layer for them. Consider Software-Defined Networking (SDN) or network overlays like VXLAN. While these technologies build sophisticated virtual networks on top of the physical infrastructure, that underlying infrastructure still relies heavily on IP addressing and, yes, VLANs for its foundational segmentation.
Automation tools, too, don’t magically bypass VLANs; they simply automate their configuration and management.
Even in the context of Zero Trust, where the focus shifts to microsegmentation at the individual workload or user level, VLANs still provide that initial macro-segmentation.
You typically place devices or users into a broad functional VLAN (e.g., “servers,” “developers,” “IoT devices”).
From there you can then create more advanced solutions. For example, Cisco ACI or VMware NSX to apply granular microsegmentation policies within or across those VLANs.
Wireless networks, too, fundamentally rely on VLANs. They allow us to map different SSIDs. For example, employee, guest, or IoT. This allows us to separate VLANs for distinct security and access policies.
The Architect’s Enduring Tool
As network architects, we live by principles of clarity, organisation, and reliability.
Trying to manage a large, flat network without VLANs would be an absolute nightmare. You could easilly expect a chaotic free-for-all that would be impossible to secure or troubleshoot effectively.
VLANs provide that essential logical framework, bringing order to what could otherwise be overwhelming complexity. They are a proven technology that simply works, reliably.
So, while networking continues to evolve at pace, and new tech emerges, the importance of VLANs remains undiminished.
They aren’t obsolete. And there’s no doubt, that they’re an enduring backbone upon which sophisticated security, automation, and cloud-native solutions are built.
We’re not abandoning VLANs; we’re leveraging them as a crucial building block in every modern, resilient, and secure network design.
