In a Mobile Ad-hoc NETwork (MANET) where Mobile Nodes (MNs) self-organize to ensure the communication over radio links, routing protocols clearly play a significant role. In future MANETs, protocols should provide routing under full mobility, power constraints, fast time-varying channels, and nodes subject to high loading. In this paper, a novel robust routing protocol, named Distributed X-layer Fastest Path (DXFP), is proposed. The protocol is based on a cross-layer metric which is robust against the time-variations of the network as far as topology (mobility), congestion of the nodes and channel quality (fading, power constraints) are concerned. All these features are integrated in a single physical cost, i.e., the network crossing time, which has to be minimized.