This paper proposes a solution to develop a 802.15.4 large-scale urban network formed by clusters, interconnected by slave-slave bridges. The solution includes a new mechanism to discover the network and optimize the coordinator election once the bridges are installed in a determined position. In addition, the solution is focused on the implementation of low-cost nodes, featuring reduced memory resources. Therefore the proposed routing solution is designed to solve the conflict between the memory resources requirements of a typical large-scale network and the low memory resources of a typical IEEE 802.15.4 commercial transceiver. Simulation results demonstrates the feasability of the proposed solution for the design of a large-scale scalable clustered network using low-cost devices.