Network elements consume 10-20% of the total power in data centers. Today's network elements are not energy-proportional and consume constant energy 1 regardless of the traffic amounts. Thus, turning off unused network switches is the most efficient way of saving energy consumption of data center networks. This paper presents Honeyguide, an energy optimizer for data center networks that not only turns off inactive switches but also increases the number of inactive switches for energy-efficiency. To this end, Honeyguide combines two techniques: 1) virtual machine (VM) and traffic consolidation, and 2) a slight extension to existing tree-based topologies. Honeyguide has the following advantages. VM consolidation, which is gracefully combined with traffic consolidation, can handle severe requirements on fault tolerance. It can be introduced into existing data centers without replacing already-deployed tree-based topologies. Our simulation results demonstrate that Honeyguide can save more energy consumption of network elements than conventional VM migration schemes, and the savings are up to 7.8% in a fat tree with k 12.