Thereafter, it is judged whether or not the source MAC address obtained at the above-described step S028 exists in a reference table (see the step S030 in FIG. 2). [0102] Incidentally, the reference table is a table in each of the wireless interconnecting devices 5, 6A and 6B, showing relationships of various administrative information on each of the wireless terminals 7 a to 7 g which are under t