What is a trunk port, and how does it differ from an access port?

• A. A trunk carries multiple VLANs using tags.
• B. A trunk carries a single VLAN using untagged frames.
• C. An access port carries multiple VLANs using tags.
• D. An access port carries a single untagged VLAN.

Answer: (A)

A trunk port is designed to carry traffic for multiple VLANs over a single physical link by tagging each frame with its VLAN ID (using tags like 802.1Q). This tagging lets switches distinguish which VLAN each frame belongs to as it traverses between devices, such as between switches or toward a router. An end device, on the other hand, connects through an access port, which is assigned to one specific VLAN and sends untagged frames to that device; the switch places those frames into the designated VLAN.

So, the trunk’s purpose is to multiplex several VLANs on one link using tags, which is why it’s the best description. The other statements describe scenarios that don’t match how trunks and access ports operate: trunks do not carry a single untagged VLAN, and access ports are not used to carry multiple VLANs with tags.