Trunkpoorten

Trunkpoorten are switch ports configured to carry traffic for multiple VLANs by using VLAN tagging, commonly 802.1Q. They are essential for interconnecting switches, routers, and other network devices in a local area network, allowing a single physical link to transport several separate network segments.

Operation on a trunk port involves tagging frames with their VLAN identifier as they pass through the link. The receiving device uses the tag to place each frame in the correct VLAN. A native VLAN may be configured so that frames for that VLAN are sent untagged. On the opposite end, the trunk must use a matching VLAN configuration so that tagged frames are correctly interpreted.

Configuration and best practices include setting the interface to trunk mode on both ends, defining which VLANs are allowed to traverse the link, and ensuring the native VLAN IDs match. It is common to disable dynamic trunking protocol (DTP) for security, and to configure trunks manually to prevent unexpected changes. Consistency of VLAN IDs and tagging across devices is essential to avoid connectivity issues.

Security considerations address risks such as VLAN hopping and misconfigurations. Mitigations include disabling DTP, restricting allowed VLANs on the trunk, using separate management networks, and ensuring proper native VLAN handling. Regular auditing of trunk configurations helps prevent accidental exposure of internal VLANs.

Typical use cases include uplinks between switches in access, distribution, and core layers, as well as connections from switches to routers or wireless controllers. Trunk ports are contrasted with access ports, which carry traffic for a single VLAN; trunks enable scalable inter-VLAN routing and broader network segmentation.