The largest part of routers and switches, today deployed in production networks, has very limited energy saving capabilities, and substantially requires the same amount of energy both when working at full speed or when being idle. To dynamically adapt such energy requirements to the real device work load, current approaches foster the introduction of low power idle and power scaling primitives in entire devices, internal components, and network interfaces. Starting from these considerations, we focus on power scaling, and we propose an analysis of the theoretical and technological limitations in adopting such kind of mechanisms. Thus, our contribution is twofold. On one hand, we performed several tests to identify the technological limitations in a software router based on off-the-shelf hardware, which already includes such capabilities. The results achieved show that the power scaling allows a linear trade-off between consumption and network performance, but the time to switch between two power states may cause a nonnegligible service interruption. On the other hand, regarding the theoretical limitations, we consider the trade-off between the benefit in dynamically adapting the power states within short time-scales and the overhead needed to choose and select the new power state.