1. A spanning tree bypassing method comprising the steps of: (a) in a first node, sending a first frame, whose destination address is a first address and whose source address is a second address, out on a designated port as well as on a root port when the first frame is received, provided that learning is done so as to send any frame destined for the first address out on the root port; and (b) in a second node having received the first frame on a blocking port, sending a second frame, whose destination address is the second address, out on the blocking port when the second frame is received.