Cyber-Physical Systems (smart grids, cities, homes, etc) are composed of computing resources, actuators and sensors , connected through IP networks. These IP networks involve many technologies. In order to help designing and evaluating these systems, we are studying the modeling and simulation of IP networks in this context. Since there is no universal IP simulator proposing a model library corresponding to all the required technologies, we propose a solution to make different major IP simulators, generally not interoperable, interact with one another in a same co-simulation. Moreover, they should also interact with simu-lators corresponding to other fields of expertise involved in the simulation, mostly related to the physical or social aspects of these systems (e.g. power models, traffic models, weather models, etc). In this paper, we propose to address these issues as a multi-modeling problem, by integrating well-known IP network simulators into a DEVS-based co-simulation platform. We propose some concepts, helping to split a network topology into several models, to create input/output ports inside them, and to integrate them to a DEVS multi-model. We illustrate our solution thanks to a use case, including interconnected event-based models executed both by NS-3 and OMNeT++, equation-based models and the co-simulation platform MECSYCO.