In Mobile Ad-hoc NETwork (MANET), every node could become active dynamically. Therefore, those nodes will affect the stability of network topology because of clustering and de-clustering, and continuously make reconfiguration for the groups of network, all that will influence the overall function of network. How to choose a cluster manager to keep the stability of network topology is an important issue. In this paper, a mechanism for the designation of clustering and cluster manager is given by MANET. The mechanism is named as Unified Framework Clustering Mechanism (UFCM for short), which is a kind of processing mechanism under consideration in multi-network service, such as processing mode of initial state in the network system, processing mode of access of nodes in the group, and the processing mode concerned on failing to manage the group because the cluster manager is erroneous. Beyond that, we also propose a backup manager to take the work of the cluster manager when the cluster manager fails.