Fog computing is a promising concept in the context of IoT, where storing and processing capabilities are decentralized to the edges of the network. However, current gateways cannot support this new paradigm, as they do not provide the necessary hardware, software and communication protocols to implement it efficiently. This paper describes the concept of a reconfigurable gateway, with a generic design, which is able to collect data, process them locally, and communicate with a network of gateways to allow distributed processing. A prototype of such a gateway is realized to demonstrate its capabilities.