Inferring the topology of the Internet is not a trivial task due to the immense scale of the Internet, its continuous evolution, and its distributed administration. At the same time, the inference of this topology is of particular importance for network operators and users. It guarantees an efficient operation of the network and a better tuning of its protocols and applications. For this reason, we survey in this work the body of the literature that deals with Internet topology inference. We classify the works based on their belonging to either the active or passive approach and we provide a summary of the main measurement tools in this field.