The next generation Internet (also known as Internet-of-Things - IoT), will ubiquitously integrate trillions of computing devices of all kinds, shapes and sizes. For this ubiquity to materialize, a key aspect will certainly be interoperability, the capability of different technologies (e.g. different communication protocols at both horizontal and vertical levels, different hardware platforms, different operating systems, fixed and mobile nodes, etc) to talk to and understand each other. A major enabler for this interoperability is the use of standard and commercial-off-the-shelf technologies (e.g. communication protocols, hardware platforms, operating systems). As IPv6 has become the de-facto communication technology for the Internet, 6LoWPAN has recently started paving the way for extending the Internet to low-power low-cost wireless devices. However, while mobility support will be a requirement (or at least beneficial) in many applications contexts, the support of mobile nodes in the default 6loWPAN/RPL protocol leads to excessive packet loss and delays. In this work, we show that interoperability between fixed and mobile nodes can be successfully achieved through the use of appropriate hand-off and topology management techniques. We propose a mobility management framework (dubbed mRPL+) unifying two hand-off models: (1) hard hand-off, where a mobile node has to break a link before finding a new link, and (2) soft hand-off, where a mobile node selects the new link before disconnecting from the current one. Importantly, mRPL+ is integrated in the 6LoWPAN/RPL stack in a backward compatible manner. Simulation results indicate that in a network with mobile nodes, packet delivery ratio with mRPL+ is nearly 100%, where RPL achieves 80% in best case. Hand-off process has a disconnected period of few milliseconds (hand-off delay = 4 ms), while RPL experiences few seconds of disconnection during node's mobility (3 - 10 s). (C) 2017 Elsevier B.V. All rights reserved.