In the following work we present a portable Ethernet frame analyzer for monitoring and managing IEEE 802.3 Ethernet - Fast Ethernet networks. The system is based on a 8 bit high performance microcontroller and one Fast Ethernet controller interface which supports 10 and 100 Mbps. The equipment could be able to capture all the circulating Ethernet packets in a network and make tasks like: traffic analysis, network statistics, network utilization, and traffic generation. The results of every task can be visualized in two modes: by a liquid crystal screen (lcd) or by a terminal using a serial connection to the personal computer. The portable system has built- in a matrix keyboard to configure and select the desired tasks; also the system has a serial port to connect to a personal computer to visualize in more detail the results of every task. The system can be programmed using the JTAG interface for future updates. of the portable system . Finally, the system has programmed a small TCP/IP stack for future enhancements like visualization using web-browser or telnet applications.