A system (100, 600) running a device within a data center, comprising: a first table comprising forwarding information of at least one station corresponding to an overlay network structure; a second table comprising forwarding information of at least one station corresponding to an underlay network structure; and a controller, coupled to the first and second tables (205A and 205B), configured for: receiving a packet; computing a specific overlay forwarding path or tree and a specific underlay forwarding path or tree according to the first table, the second table, and a destination to transmit the packet; obtaining information of an overlay next hop station and information of an underlay next hop station according to the specific overlay forwarding path or tree and the specific underlay forwarding path or tree; and performing packet encapsulation and transmission for the packet according to the information of the overlay next hop station and the information of the underlay next hop station, characterized in that the first and second tables (205A and 205B) are stored within a single dual-port storage device, and the controller is capable of simultaneously looking up the first table and the second table within the single dual-port storage device, wherein the controller is simultaneously looking up the second table for a previous packet and the first table for a next packet. a first table comprising forwarding information of at least one station corresponding to an overlay network structure; a second table comprising forwarding information of at least one station corresponding to an underlay network structure; and a controller, coupled to the first and second tables (205A and 205B), configured for: receiving a packet; computing a specific overlay forwarding path or tree and a specific underlay forwarding path or tree according to the first table, the second table, and a destination to transmit the packet; obtaining information of an overlay next hop station and information of an underlay next hop station according to the specific overlay forwarding path or tree and the specific underlay forwarding path or tree; and performing packet encapsulation and transmission for the packet according to the information of the overlay next hop station and the information of the underlay next hop station, receiving a packet; computing a specific overlay forwarding path or tree and a specific underlay forwarding path or tree according to the first table, the second table, and a destination to transmit the packet; obtaining information of an overlay next hop station and information of an underlay next hop station according to the specific overlay forwarding path or tree and the specific underlay forwarding path or tree; and performing packet encapsulation and transmission for the packet according to the information of the overlay next hop station and the information of the underlay next hop station, characterized in that the first and second tables (205A and 205B) are stored within a single dual-port storage device, and the controller is capable of simultaneously looking up the first table and the second table within the single dual-port storage device, wherein the controller is simultaneously looking up the second table for a previous packet and the first table for a next packet. the first and second tables (205A and 205B) are stored within a single dual-port storage device, and the controller is capable of simultaneously looking up the first table and the second table within the single dual-port storage device, wherein the controller is simultaneously looking up the second table for a previous packet and the first table for a next packet.