What is a VLAN and why is it used?

• A. A virtual LAN that segments a network at Layer 2 to improve security, reduce broadcasts, and organize traffic.
• B. A physical network segment.
• C. A technology to extend broadcasts.
• D. A security protocol.

Answer: (A)

A VLAN creates multiple logical networks on the same physical infrastructure by grouping switch ports into separate broadcast domains at Layer 2. This means devices in the same VLAN can talk directly at Layer 2, while devices in different VLANs cannot see each other’s broadcasts, which reduces unnecessary traffic and congestion. By isolating groups from one another, VLANs also improve security since devices in different VLANs aren’t exposed to each other unless you enable inter-VLAN routing.

Organizationally, VLANs make network management easier because you can group devices by function, department, or project regardless of their physical location. When devices in different VLANs need to communicate, a router or Layer 3 switch performs inter-VLAN routing.

VLANs are not just a physical network segment since they’re virtual and can span multiple switches; they don’t extend broadcasts—in fact, they limit them to each VLAN. They’re not a security protocol; they’re a method of segmentation and tagging (often using 802.1Q) to carry multiple VLANs over trunk links.