VLAN
A Virtual LAN that logically segments a switch into separate broadcast domains.
A VLAN (Virtual LAN) partitions a physical switch into multiple logical broadcast domains using IEEE 802.1Q tagging, so frames carry a 12-bit VLAN ID (1–4094 usable) as they traverse trunk links between switches. Devices in different VLANs cannot communicate directly even if they share the same physical hardware, which contains broadcast storms and confines sensitive traffic — such as voice or management traffic — to its own segment.
The critical exam distinction is that VLANs operate at Layer 2 and provide isolation, but routing between VLANs still requires a Layer 3 device. A common trap: adding a host to a different VLAN on the same switch does not automatically grant it network access — the router or Layer 3 switch must have a corresponding interface or subinterface configured for that VLAN.
PlayPrepHQ study notes are written and reviewed against primary exam sources. How we create & review content →