Within the field of automation technology the use of Industrial Ethernet is rising. This in turn demands devices capable of precisely recording, analyzing, and manipulating communication data for diagnostic purposes. Existing solutions so far lack required flexibility or are unable to cope with sustained Gigabit-per-second data streams. This is especially true for general-purpose approaches employing ordinary network adapters and plain software-based analysis. In this paper we describe a flexible and lightweight network agent for real-time, high-performance networks. This agent is capable of handling sustained data rates up to 2x 1GBit/s while offering real-time event-triggers, 10ns-resolution timestamps, real-time filtering, and statistics functions. An auxiliary processing unit as well as a modular software environment allow customization for a variety of tasks. The agent is realized as a dual processor SoC design on a Xilinx Virtex-II Pro FPGA. Categories and Subject Descriptor...