The use of overlapping decompositions in designing routing controllers for large-scale networks is considered and a decentralized dynamic routing controller design strategy is proposed. The strategy is based on the overlapping decompositions method and can be used for large-scale networks which have more than two overlapping subnetworks and/or have more than one node in the overlapping part. The controller obtained by the proposed strategy is decentralized in the sense that all on-line computations can be done locally at the individual nodes without any information transfer from the other nodes. The controller satisfies all the routing control constraints and it avoids any looping. The controller also clears the queues in finite time in the absence of external arrivals and it keeps the queue lengths bounded in the presence of external arrival rates which do not exceed a certain maximum rate. In order to illustrate the proposed controller's performance, the controller is applied to an example network and some simulation results are presented in a number of cases. Furthermore, a centrally designed controller is also applied to the same network for the same cases, in order to obtain a basis for comparison.