Abstract: The fault-tolerant network management system is a hierarchical system having two Manager-of-Managers (MoM) that are implemented at the highest layer in an active-passive mode. A middle layer includes Mid-Level Managers (MLMs), which are used to manage agents disposed throughout different areas of the network at the lowest layer. The MLMs relieve the MoM from dealing with individual agents, and hence enhance the scalability of the whole Network Management Systems. MLMs are configured to work in pairs, where each pair includes two MLMs working in an active-active mode. The MoMs and MLMs have the capability of backing each other up in the case of a failure.