carrier VLAN

In STP (Spanning Tree Protocol), carrier VLAN (Virtual LAN)s define the scope of the STPD (Spanning Tree Domain), including the physical and logical ports that belong to the STPD as well as the 802.1Q tags used to transport EMISTP- or PVST+-encapsulated BPDUs. Only one carrier VLAN can exist in any given STPD.