[en] For a long time, traceroute measurements combined with alias resolution methods have been the sole way to collect Internet router level maps. Recently, a new approach has been introduced with the use of a multicast management tool, mrinfo, and a recursive probing scheme. In this paper, after analyzing advantages and drawbacks of probing approaches based on traceroute and mrinfo, we propose a hybrid discovery tool, MERLIN (MEasure the Router Level of the INternet), mixing mrinfo and traceroute probes. Using a central server controlling a set of distributed vantage points in order to increase the exploration coverage while limiting the probing redundancy, the purpose of MERLIN is to provide an accurate router level map inside a targeted Autonomous System (AS). MERLIN also takes advantage of alias resolution methods to reconnect scattered mul- ticast components. To evaluate the performance of MERLIN, we report experimental results describing its efficiency in topology exploration and reconstruction of several ASes.