The increasing complexity of automotive networks, their challenging timing constraints and their high bandwidth demands require new concepts for future in-car communication. Real-time Ethernet is meant to be a suitable candidate for the next-generation in-car interconnection. However, model-based testing capabilities must be available as well. Applications must be validated prior the first assembly, due to the distributed development process. Methods like residual bus simulation are of particular interest to allow for testing systems in early development stages by emulating unfinished or not available parts of the system. In this paper, we present a methodology and a feasibility study of a residual bus simulation in automotive real-time Ethernet systems. The challenges of applying this testing method in real-time Ethernet based networks with parallel packet transmission are outlined and compared to today's automotive bus system simulation approaches. Furthermore, the combination of different model-based testing techniques, that are not used in state-of-the-art commercial tools, are applied for the validation of non-functional timing requirements. An extension to an existing abstract test case model is proposed, which allows modelling temporal attributes. It is simultaneously used as simulation model to drive the residual bus simulation. We demonstrate the approach's feasibility by implementing a prototype residual bus simulator for real-time Ethernet networks and applying it to an example application.