Ethernet has been used for interconnection networks of high-performance computing (HPC) systems that include PC clusters. Although a layer-2 Ethernet topology is limited to a tree structure in order to avoid broadcast storms and deadlocks of frames, various topologies with deadlock-free routing, that include loops, suitable for parallel processing can be used by the application of IEEE 802.1Q VLAN technology. However, their performance and power evaluations on real PC clusters with Ethernet have been rarely done. Thus, their evaluation on real PC clusters with Ethernet is important to analyze their impact on the total systems and validate their simulation results. In this paper, firstly we measure tree, and fully connected topologies with link aggregation on a 66-node/528-core PC cluster with a number of Ethernet switches. Secondly, we measure the optimization of the power consumption of Ethernet by a power-aware link regulation in order to reduce the power consumption of Ethernet switches on a real PC cluster. Measurement results show that the fully connected topology achieves 3.21 TFlops in High-Performance Linpack Benchmark (HPL), and its Rmax/Rpeak value is 67%. Up to 23% of the power consumption of networks can be reduced by the power-aware link regulation, while the performance is degraded by less than 1%.