In support of continuously increasing line rates and various Internet services, multiprocessor-based linecards have appeared in next-generation routers, significantly improving performance. However, this improvement has come at the expense of increased energy consumption, which tends to not only raise the operational and cooling costs, but also lower the reliability of the router. In this article, we present a simple and yet effective Dynamic Voltage Scaling (DVS)-oriented scheme for energy-efficient operations of multiprocessor-based linecards. We prove that for a given task and a timing constraint, those processors in a linecard consume less energy when operating at the same voltage than operating at different voltages. Additionally, we derive the optimal configuration for minimal energy consumption in multiprocessor-based linecards and also show how it can be extended for general-purpose multiprocessor systems.