What is the main purpose of a VLAN in a LAN?

• A. To increase network throughput by adding more switches.
• B. To logically segment a LAN into separate broadcast domains to improve security and reduce broadcast domains.
• C. To connect multiple VLANs into a single broadcast domain.
• D. To assign IP addresses automatically.

Answer: (B)

A VLAN partitions a LAN into separate broadcast domains, which is its main purpose. By grouping devices into logical segments, broadcasts stay contained within each VLAN, reducing unnecessary traffic and allowing you apply security and access policies per segment. If devices in different VLANs need to communicate, inter-VLAN routing through a router or layer-3 switch is used.

The option about increasing throughput by adding more switches isn’t the primary goal of a VLAN; while VLANs can help manage traffic, they’re about segmentation and reducing broadcast domains, not boosting raw bandwidth. The idea of merging multiple VLANs into a single broadcast domain goes against how VLANs work—broadcasts are deliberately kept separate and only cross via routing. Automatically assigning IP addresses isn’t a VLAN function; DHCP assigns IPs and can operate within or across VLANs, but that’s a separate mechanism from the segmentation VLANs provide.