We presented an architecture where the subsystem allows host unaware network service for manageability. In our prototype implementation, we used an ARM-based board and a 3G network device. Then, we evaluated and showed the results and data measured from an actual network environment. First, the host system can communicate without noticing the existence of the subsystem. Then, from the measurement data, we determined that the processor of the subsystem should run at more than 72 [MHz]. Second, the two bridge methods could direct the incoming data to the subsystem and host system, and consolidate the outgoing data from the subsystem and host system. Third, some applications on the subsystem can maintain network service without relation to the power state of the host system; hence, it can deal with priority tasks in a short period. Fourth, the subsystem with a network device works with reasonable power consumption. We confirmed that a power reduction of about 60% can be achieved while downloading. New products for both ARM CPU and network devices with less power consumption are available. Therefore, by replacing only these components, energy utilization can be further improved. In summary, the proposed architecture achieves host unaware network services without requiring any modifications to the network components. We prototyped and confirmed its feasibility in a real environment.