What is the native VLAN on a trunk?

• A. The untagged VLAN on a trunk; mismatches cause traffic leaks.
• B. The VLAN that carries all tagged traffic by default.
• C. The VLAN used to segment management traffic on access ports.
• D. The VLAN assigned to every port by default.

Answer: (A)

On a trunk, the native VLAN is the one whose frames are sent untagged. The switch treats any untagged frame on that link as belonging to the native VLAN, while all other traffic is carried with VLAN tags. This matters because if the native VLAN is different on each end of the trunk, untagged frames can be mapped to different VLANs on the two sides, leading to traffic leaks between VLANs or misdelivery of frames. The other statements don’t fit because tagged frames carry specific VLAN IDs, management traffic is not defined by the native VLAN, and not every port is assigned the same default VLAN.