CyberGuard dictionary / Network Security
Virtual Local Area Network
A virtual local area network is a logical grouping of network ports and traffic within a bridged network, independent of physical cabling.
In simple terms
VLANs let one set of switches carry separate logical networks, such as guest devices and staff workstations.
Technical explanation
IEEE 802.1Q identifies VLAN membership on tagged Ethernet frames. Traffic between VLANs normally requires routing and explicit policy; a VLAN by itself does not prevent every lateral movement or configuration error.
A VLAN separates layer-two broadcast domains on shared switching hardware. Routing and firewall rules determine traffic between VLANs, so VLAN assignment alone is not a full trust boundary.
Examples in practice
An office uses one switch infrastructure but places visitor Wi-Fi traffic in a different VLAN from payroll workstations.
Guest and staff ports belong to different VLANs, while a firewall controls access between them. A test confirms guests cannot reach staff file shares even when using the same physical switch.
Why it matters
VLANs support segmentation when routing rules and switch configuration enforce the intended boundaries.
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Sources and further reading
Published 2026-10-15 · Last updated 2026-10-15 · CyberGuard editorial content. Source links provide context; they do not imply endorsement.