In this paper, we propose an analysis of three-level network topologies, in the context of the topological optimization problem of Internet protocol (IP) networks. This problem consists in selecting the number of routers and their types to install at each level, selecting the port types to install in each router and finding the access, edge and core networks. Considering that IP networks are still expensive, network optimization is an important issue for the service providers to remain competitive. A mathematical programming model is proposed for this problem. Next, the model is adapted and analyzed for each topology considered. An illustrative example is solved using a commercial implementation of the branch-and-bound algorithm.Index Terms-Internet protocol (IP) networks, three-level networks, access, edge and core networks, branch-and-bound.