The present invention addresses method, apparatus and computer program product for enabling improved coexistence of Software Defined Network, Network Function Virtualization, and legacy networks. Thereby, information about characteristics of available core network nodes is obtained, it is determined, upon receiving a signaling request from a network node, which type of network node the signaling network node is, among at least a legacy network node, a virtualized network node and a software defined networking network node, and at least one network node to be used as gateway is selected from the available core network nodes, according to the determined type of signaling/originating network node and a policy set in advance for minimizing traffic load.