An apparatus and a method are provided by which, in an apparatus for setting up and maintaining network functions, identities of first type network functions and second type network functions are stored, wherein the first type of virtual network functions are configured to select one or more of the second type network functions, and, for each first type network function, information regarding second type network functions which are selectable by the corresponding first type network function based on information regarding physical conditions of the first type network functions and the second type of virtual network functions are maintained.