Abstract: The present invention relates to a method (10) for determining the optimal configuration of apparatuses of a fixed telecommunication network organised on two hierarchical layers, i.e. of a network comprising access nodes and transit 10 nodes. The method (10) based on the location of the access nodes (20), on their homing mode (30) and of the traffic exchanged between them (40), of the candidate locations for the installation of the transit apparatuses (50), of the capacity and cost parameters of the transit apparatuses (60), 15 of the capacity and cost parameters of the connections (70) and of the general parameters and grade of service offered (80), allows to determine the network structure with the lowest construction cost, i.e.