A redundant path configuration method and a control method are disclosed. An intercommunication path for mutually transmitting and receiving a signal is provided among the BHEs each of which is a top of a tree. When failures occur in an active system path in certain AE, a standby system path (BHE) relays communication between the AE and the (active system) BHE so as to secure continuity of communication. The intercommunication path through which a data signal does not flow in a normal operation is used as a traffic accommodation path in an emergency among the BHEs. By setting a bypass between the tops of the trees, when a failure occurs in one tree, a signal is transferred from the active system BHE to the standby system path in which another BHE is a top to build a sub-tree bypassing the failure point and to secure a communication path.