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Before VLANs, segmentation meant more physical switches. Want a separate network for finance? Buy another switch. Want to move a user to a different network? Move their cable. VLANs let you do both in software, on the same physical hardware — which is why every enterprise has them and every CCNA candidate must master them.
Notice the word 'broadcast' throughout. VLANs are fundamentally about broadcast domain boundaries. A broadcast sent by a host in VLAN 10 doesn't reach hosts in VLAN 20, even if they're plugged into adjacent ports on the same switch.
| Type | Purpose | Typical ID |
|---|---|---|
| Data | User workstations and general traffic | Any (usually 10–100) |
| Voice | IP phones — separated for QoS and security | Any (often 100–200) |
| Management | Switch/router management access | Usually 1 or a dedicated VLAN |
| Native | Untagged traffic on a trunk | Default 1, often changed |
| Blackhole/unused | Ports assigned to a nonexistent VLAN, effectively disabled | Any unused ID |
The term 'VLAN 1' comes up constantly because it's the default VLAN — every port starts in it, and any untagged traffic on a trunk defaults to it. Best practice is to move management to a dedicated VLAN and leave VLAN 1 unused for anything important.
Valid user VLANs are 2–1001 in the standard range, and 1006–4094 in the extended range. Extended-range VLANs require VTP transparent mode or VTP version 3 — a nuance you'll hit if you're configuring large VLAN counts.
Four VLANs on one switch means four broadcast domains. Devices within the same VLAN communicate via Layer 2 (switching). Devices in different VLANs need a router or Layer 3 switch to communicate — which is where Section 9 (Inter-VLAN Routing) comes in.
VLANs are the foundation of every modern campus. Understand the broadcast-domain model and you understand why they exist. Configure them badly and you'll spend nights chasing weird connectivity issues. Get them right and everything else builds cleanly on top.
Next lesson: configuring access ports and assigning them to VLANs.
Finish the lesson once you have worked through the material. This awards ★ 30 XP.