Injection-locked Fabry-Perot (IL-FP) lasers have extensive range of attractive applications. For example, in terms of telecommunication-based applications, IL-FP lasers were proposed in Radio-over-Fiber (RoF) systems. In addition to this, injection locking was used to realize improved CATV transmission. Moreover, IL-FP lasers can provide more cost- and complexity-effective solution for optical transmitters in the wavelength division multiplexed passive optical networks (WDM-PONs), since they can substitute tunable lasers in each subscriber. Furthermore, injection locking offers a broad spectrum of peculiar nonlinear effects which may provide attractive and efficient solutions for building blocks in optical signal processing systems. For example, optical bistability in injection-locked laser diodes finds its use in optical switches, fast low-power memories, regenerators, or all-optical flip-flops, which can serve as the storage for packet header information and can be used in shift registers, counters, regenerative memory circuits, etc. We present a full-scale multimode rate equation model of an IL-FP laser, analyze its stability and present new stability map. We recognize the region of the dispersive bistability, and within this region, we propose two optical switching methods, which could be employed in the realization of an all-optical flip-flop. We analyze switching times and propose methods for switching time optimization.