Net-Controller is a user-friendly network visualization and management tool developed at EPFL in order to easily retrieve and display in real time network statistics, such as link throughput and queue occupancy from a large testbed composed of wireless routers. Additionally, Net-Controller allows to control and modify the parameters of a complete network from a central point, and to easily generate traffic between different nodes. We intend to illustrate some of the features of Net-Controller through two examples that show how easily this tool detects and helps elucidate the throughput degradation that occurs in a wireless multi-hop network. The first example shows how and why fair queuing  improves performance compared to the standard FIFO policy used in off-the-shelf routers. The second example shows how and why a hop-by-hop congestion control mechanism, such as EZ-Flow  is needed to tackle the instability problem of a multi-hop scenario.