A fundamental issue impacting the performance of mobile ad hoc networks is the wireless interference among neighboring nodes. In this paper, we derive an interference aware metric NAVC based on the information collected from the IEEE 802.11 Medium Access Control (MAC) layer. We then propose a novel Dynamic Interference Aware Routing protocol (DIAR) building on NAVC and AODV [3]. Both mathematical analysis and experimental study indicate that NAVC can effectively predict available bandwidth and delay. Simulation results indicate that the overall system performance can be improved by DIAR compared to AODV.