A method and apparatus for determining a network topology of a hierarchical network, the apparatus including: a memory unit to store an outage state matrix representing an outage state of leaf nodes at the lowest hierarchical level of the hierarchical network; and a processing unit to decompose the stored state matrix into a first probability matrix indicating for each inner node of the hierarchical network the probability that the respective inner node forms the origin of an outage at the lowest hierarchical level of the hierarchical network and into a second probability matrix indicating for each leaf node at the lowest hierarchical level of the hierarchical network the probability that an inner node forms a hierarchical superordinate node of the respective leaf node at the lowest hierarchical level of the hierarchical network, wherein the decomposed second probability matrix is evaluated by the processing unit to determine the network topology.