Active networks enable customization of network functionality without the lengthy standard-mediated committee processes. Most of the works in the literature utilize the capsules or active packets as the means to transfer code information across active networks. In this paper, we propose an active network infrastructure based on mobile agents technologies. In our prototype implementation, mobile agents are the building blocks of carrying functional customizations, and the active nodes offer software application layers, the Agent Servers, to process mobile agent-specific customizations to facilitate network functionality. Both integrated and discrete operational models of network customizations are supported. In addition, for the application-specific protocol development and deployment, an abstract protocol structure and a protocol loading mechanism are presented. Furthermore, we provide an agent management/control mechanism and devise a protocol management/control mechanism. As a result, improved network functionality can be achieved.