The MOMBASA Software Environment is a toolkit that implements mobility-related functionalities complementing multicast protocols for multicast-based mobility support. The functionalities provided by the MOMBASA Software Environment include detection of link availability, registration, location update, paging, address translation, handoff initiation, handoff control, rerouting, prevention of handoff oscillation and inactive handoff suppression. The MOMBASA Software Environment is targeted for researchers investigating the support of host mobility in IP-based cellular networks. It aims at performance evaluation of mobility support by means of measurements. The software is easy to maintain, to configure and to extend: a) It has a clear design, b) it provides well-defined configuration and management interfaces, c) policies can be used to control and tune the system behavior and d) it has a generic interface to the multicast which facilitates to investigate multicast protocols of different types. This paper describes the functionalities, features and structure of the MOMBASA Software Environment and presents a framework for evaluating the performance of mobility support using the MOMBASA Software Environment. The MOMBASA Software Environment is open software under GNU Public License. It is freely available, extensively tested and well documented.