Fieldbuses represent the lower communication layers of industrial communication systems. There are large efforts in standardisation and in the introduction of open fieldbus protocols. However, users, manufacturers and first of all system integrators of fieldbuses have to support not only a single fieldbus, but a number of different systems. The enormous efforts in preparation, management and training reduce the economic advantages of fieldbus use. There is a global agreement that there will be no universal fieldbus during the next years, due to the different requirements of the technical processes. This fact has caused an increasing research on universal concepts and solutions that will reduce the efforts in preparation, configuration, installation and management of heterogeneous industrial communication networks, relying on more than one fieldbus. In addition, the integration of the systems into existing LAN-based enterprise networks is important for future developments. The article shows appropriate concepts and implementations for heterogeneous networks based on open fieldbus systems.