LHCb employs two large networks based on Ethernet. One is a data network dedicated for data acquisition, the other one is a control network which connects all devices in LHCb. Sophisticated monitoring of both networks at all levels is essential for the successful operation of the experiment. LHCb uses a commercial SCADA system (PVSSII) for its Experiment Control System (ECS). For the consistency and efficiency reason, the network management system is implemented in the same framework. We show here how a large scale network can be monitored and managed using tools originally made for industrial supervisory control, and discuss several tools developed to facilitate the integration of network management and monitoring in LHCb's control system. In the network management system, the status of the network is monitored at different levels, including the application level, the devices, the ports and the connectivities. Alarms can be issued to inform the experiment operators and online network experts about errors such as dropped packets or broadcast-storms. Reports and long-term monitoring are possible by using powerful trending tools.