An ad hoc network is an autonomous system of wireless mobile nodes, in which each node forwards packets for other nodes so that nodes out of direct wireless transmission range can communicate. In on-demand routing protocols for ad hoc networks, we find that existing schemes mistakenly may decide that a link is broken when it is not, especially when either endpoint node of the link experiences heavy interference. Moreover, a route claimed to be available may contain broken links due to the presence of stale routing information. We develop interference-aware enhancements both at the MAC layer and at the routing layer to address these problems. Simulation results show that our proposed enhancements reduce the problem dramatically and in turn increase the performance and efficiency of the routing protocol. In our simulations, total network throughput improved by up to 38% with DSR and by up to 13% with AODV.