VLAN
Also known as: Virtual LAN
A VLAN (Virtual LAN) splits one physical network into several logically separate networks on the same switch.
A VLAN (Virtual LAN, defined in IEEE 802.1Q) divides a single physical network into multiple logically separate networks without requiring extra cabling or switches. Every device belongs to one VLAN, and traffic stays inside that group even when devices share the same physical switch. This makes it possible to keep parts of a network apart for operational or security reasons.
In practice, each switch port or Wi-Fi network is assigned a VLAN ID, often a number such as VLAN 10 for office PCs or VLAN 20 for cameras. Links between switches carry several VLANs at once over a single cable by tagging every Ethernet frame with its VLAN ID. Without a router or firewall explicitly connecting the VLANs, devices in different VLANs cannot reach each other.
A common misunderstanding is treating VLANs as a security control on their own — they only separate ordinary traffic. A missing or misconfigured firewall rule between VLANs can silently reopen that separation, or block traffic that should be allowed. VLAN IDs are also easy to duplicate or forget on a trunk port, which shows up as devices that are unexpectedly unreachable.
What it means in practice
For a business, this means office workstations, production control systems, cameras and guest Wi-Fi should run in separate VLANs so that a problem in one area doesn't automatically spread to the rest. Without that separation, it often only becomes visible once an infected laptop reaches equipment it never should have touched. NDVDL designs and configures this segmentation as part of network projects for SMEs in Vienna, Lower Austria and Slovakia.
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