This paper proposes a design in order to test Ethernet transmission rates using only one Ethernet port. According to RFC 2544 standard, throughput, latency, frame loss rate and back-to-back frame test had been applied to measure capabilities of the unit under test. The proposed design wields ZYNQ-7000 SOC with Dual-Core Cortex-A9 ARM microprocessor. Two cores of microprocessor had been separated for different tasks. One is dedicated for Ethernet frame generator, while the other one is operated Ethernet packet receiving functions and performance calculations. This dual core structure leads to measuring Ethernet communication using only one port. Therefore, this paper offers an easy to implement solution that is cheaper than commercial test equipment.