The router can have a Routing Engine in each of the slots labeled RE0 and RE1 at the rear of the chassis, as shown in Figure 2. Each Routing Engine weighs approximately 3 lb (1.5 kg). The Routing Engines are hot-pluggable, as described in Field-Replaceable Units (FRUs). For a description of the effect of removing a Routing Engine, see Routing Engine. To replace a Routing Engine, perform the following procedures: