Mobile ad hoc wireless networks have been extensively studied as they make possible various interesting future applications. However, most of the existing studies focus on showing the overall impact of mobility from topology changes and signal variations, while they do not clearly show how inter-operability among protocol layers affects the network performance. To address this issue, we developed a testbed which enables us to investigate the cross-layer interaction among protocol layers at Carnegie Mellon University (CMU). In this paper, we report on the testbed as well as on our experiences and findings from it.