A switch, an operation method thereof, and a method for updating a forwarding table thereof are provided. The method for updating the forwarding table includes receiving a packet, and determining whether the packet is one of a Join type packet and a Leave type packet for determining to adopt a first VLAN table or a second VLAN table. In the first VLAN table, a first apparatus and a second apparatus are defined in different VLANs, and in the second VLAN table, the first apparatus and the second apparatus are defined in a same VLAN. When it is determined that the packet is one of the Join type packet and the Leave type packet, the second VLAN table is adopted for updating the forwarding table for simplifying the content of the forwarding table. Further, an efficiency of the switch can be improved by using the updated forwarding table.