MIPv6 is the IPv6 based mobility management protocol and it is expected to become the mobility management protocol of choice for the Next Generation Wireless Access Networks. In order to develop the understanding of the protocol's behavior, its suitability for deploying in a wireless environment and in order to be able to propose and develop appropriate improvements and optimizations, it is imperative to have an accurate, reliable and scalable simulation model for the MIPv6 protocol which is fully compliant to the IETF standards and specifications. This paper presents the logic, design and performance results of an extensible MIPv6 (xMIPv6) simulation model integrated into the INET20061020 framework for the OMNeT++ discrete event simulator. Categories and Subject Descriptors I.6.4 [Simulation and Modeling]: Model Validation and Analysis I.6.5 [Simulation and Modeling]: Model Development