Adopting mobile agent technology can eliminate the need for the administrator to manage clusters, e.g., installation and upgrading software, and auditing clusters and networks. However, creating mobile agent-based network management systems is still in an ad-hoc manner but not methodologies for building mobile agents for cluster and grid computing. This paper presents a framework for reusable mobile agents for managing clusters in the sense that they are independent of either particular cluster systems or applications. The framework enables a mobile agent to be composed of two layered components, which are mobile agents. The first is a carrier for the second over particular networks independent of any management tasks and the latter defines management tasks performed at each host, independently of any networks. The framework also offers a mechanism for matchmaking the two components. Since the mechanism has been formulated based on a process algebra approach, it can precisely select a suitable itinerary component to do management tasks at the hosts that the tasks want to visit over networks. The framework provides a methodology for easily developing and operating mobile agents to travel among multiple clusters to conduct their management tasks at each of the clusters they visit.