trunk
termnetworking
A link that carries several VLANs at once, tagging each frame so the far end knows which network it belongs to.
The trunk is where segmentation is enforced and where it is most often quietly undone. A port configured to carry every VLAN by default hands an attacker the whole estate from one cable, and a native VLAN mismatch between two switches silently merges two networks the diagram says are separate. Both are configuration rather than protocol defects, which is why segmentation reviews look at trunk allow-lists before they look at firewall rules.
Also known as: 802.1q, tagged port