In this paper we deal with the problem of how to expand MANs (Metropolitan Area Networks) in a cost-effective way. We first propose a mathematical programming model that includes the location of new switch sites, the update of the configuration of modular switches with respect to ports and bases, the update of the access network with a star topology and the expansion of the backbone network with a multiple ring topology. Next, in order to find a good solution, we propose a tabu-based heuristic. Finally, we present an illustrative example of a MAN design with its successive expansions.