The IEEE 802.11 standard uses the Distributed Coordination Function (DCF) protocol to share the medium among multiple stations. DCF is implanted in all the mobile ad-hoc networks (MANET) simulators but its validation poses a true problem considering both the diversity of the models and their simplicity. The validation systems being hard to implement, the visualization tools represent, by comparison, auxiliary applications much more simple to develop. Behind their apparent simplicity, the graphic traces are extremely powerful teaching aids able to bring images of the DCF dysfunctions observed during the simulation execution. For this purpose, the simulation events are logged in trace files and then displayed in the form of timeline. The main contribution of this work is the definition of a tool allowing visualization of the network simulators activity at the data link layer. To show the potential of the approach, screenshots showing the dysfunctions observed in the NS-2 simulator are presented and analyzed.