Hybrid networks composed of a wireless infrastructure network providing Internet access to an underlying ad hoc network are more and more attractive due to their low installation cost. In these all-wireless environments, performance is a key issue as radio bandwidth is scarce. Handoffs management is particularly important as these networks are likely to be highly mobile. Mobility notification should therefore be optimized in order to limit signaling overhead while keeping a good reactivity against terminals mobility. This article presents and studies by simulation different level optimizations applied to a modified Cellular IP protocol.