IP network mobility has already emerged as a key domain of wireless IP networking. The network research community has taken great interest and paid considerable attention to advance IP mobility applications. Accordingly, different advanced networking mechanisms have been considered to optimize IP network mobility. One of these mechanisms is network multi-homing which has been the focus of many IP mobility studies within the academic research and IETF communities. The combination of network mobility and multi-homing has turned into a conceivable approach to effectively deal with expanding system availability and improving the performance of mobile IP network. There are many studies proposed during the recent years to realize network multi-homing for the Network Mobility Basic Support (NEMO BS) protocol, a leading IETF IP mobility protocol. This paper studies and reviews up-to-date research works in supporting multi-homing for NEMO-based mobile IP networks. The aim is to investigate the current state of multi-homing support for NEMO networks and outline recent research directions in this regard.