The present invention discloses a technical proposal that the matlab of a class tag is popped up through setting a character; the matlab is used to substitute a multi-layer tag forwarding table and asingle layer tag forwarding table needed for generating the popping up of the class tag, and a tag forwarding table is used to substitute the former a plurality of tag forwarding tables for operation,thus reducing the number of the tables in the tag forwarding table. Accordingly, the technical proposal of the present invention also provides a technical proposal of searching the tag forwarding table. By applying the technical proposal of the present invention, the number of the tables in the tag forwarding table is reduced, the cost of the hardware memory is reduced, and the speed of searchingthe tag forwarding table is improved.