Green communications has embraced data centers fully and data center operators are seeking the most effective means to minimize the energy consumption of their data center infrastructure without impacting the performance of deployed digital services. In this chapter we discuss recent techniques that have the potential to improve the energy efficiency of data center networks. We then propose a network-centric energy management solution that combines guided routing to consolidate network flows on a compact set of network elements with fine-granular sleep mode techniques, working jointly with server power management and without affecting application performance. We finally discuss measurements obtained from a simulation of an OpenFlow-based implementation showing that our approach achieves significant energy savings under typical data center application loads, especially when both server and network power management are used together.