trunk
also: trunk link, 802.1Q trunk, tagged link
In networking, a trunk is a link that carries traffic for multiple VLANs (Virtual LANs) between switches or network devices, as opposed to an access port that belongs to a single VLAN.
A trunk port is configured on network switches to transport frames from multiple VLANs over a single physical connection. This is essential in larger networks where you need to separate traffic logically without running separate cables for each VLAN.
When a frame travels on a trunk, it is tagged with a VLAN identifier (usually using 802.1Q tagging) so the receiving switch knows which VLAN it belongs to. For example, a trunk link between two switches might carry traffic for both the Finance VLAN (ID 10) and HR VLAN (ID 20) simultaneously.
Trunk ports differ from access ports, which are connected to end devices like computers or printers and handle traffic for only one VLAN. Most modern data center and enterprise network designs rely on trunks to efficiently manage multiple VLANs across infrastructure.