What is the purpose of VLAN tagging using 802.1Q?

• A. To carry traffic for multiple VLANs over a single trunk link by adding a VLAN tag.
• B. To assign IP addresses automatically.
• C. To encrypt VLAN traffic.
• D. To connect multiple VLANs into one.

Answer: (A)

802.1Q tagging lets you carry traffic for multiple VLANs over a single physical link by inserting a VLAN tag into each Ethernet frame that identifies which VLAN the frame belongs to. On access ports, frames are untagged and belong to one VLAN; on trunk ports, frames from many VLANs are tagged with their VLAN IDs, and switches use that tag to forward the frame to the appropriate VLAN. When the frame reaches the destination and exits toward an access port, the tag is removed. This tagging mechanism enables efficient use of the network’s physical infrastructure while keeping traffic separated by VLAN. It isn’t about automatically assigning IPs, encrypting traffic, or merging VLANs into one.