Abstract— This paper examines mobility events, and particularly handovers in an overlay environment, where Hierarchical Mobile IP is operating over MPLS. The overlay operation is examined in detail under two scenarios and a comprehensive explanation of the operation of intra- and inter-cell handovers is presented. Furthermore, it improves on existing methods of MIP-MPLS interworking first by defining a simple framework based on Hierarchical Mobile IPv6 (HMIPv6), and second by outlining the relevant protocol design aspects.