Abstract The routing protocols designed for wired networks can hardly be used for mobile ad hoc networks due to unpredictable topology changes, and thus several routing protocols for mobile ad hoc networks have been proposed. The goal of this chapter is to select the most reliable route that is impervious to failures due to topological changes caused by host mobility. To select a reliable route, we introduce the concept of stable zone and caution zone and then apply it to the route discovery procedure of the existing ad hoc routing protocols. The concept of the stable zone and caution zone, which are located in a mobile node’s transmission range, is based on a mobile node’s location and mobility information received by the Global Positioning System (GPS). We evaluated the proposed algorithms by simulation in various conditions, and we obtained an improved performance in route maintenance time, the number of route disconnections, and packet delivery ratio.