In the near future, vehicles are expected to become a part of the Internet, either as a terminal in a mobile network, as a network node, or as a moving sensor (providing environmental information, cars status, streaming video, etc.) or a combination of the three. This is partly due to the steadily growing interest of vehicles' passengers in location-based information. Drivers and passengers that would want to receive information about traffic jams or accidents in their vicinity will likely be interested in accessing Internet services from within the vehicular network. Access can be gained by using roadside installed Internet Gateways (IGs), which are able to communicate with the vehicles. However, several difficulties must be addressed in such a scenario. Examples are the communication efficiency, mobility support, the discovery of Internet Gateways, and the handover of connections from one gateway to the next. In this paper, we are focusing on the aspect of accessing the Internet from within the vehicle network using a service discovery protocol. We therefore developed a Dynamic Discovery Service (DDS) protocol to discover Internet Gateways which is suitable for the characteristics of future vehicular ad hoc networks. Besides the benefit of efficient service discovery, our protocol is able to choose the most suitable Internet Gateway among others.