Abstract—Most devices are nowadays connected automatically via an IPv6 address. IPv6 was developed in 1998 so that the IPv4 address space issues are solved. Due to rapid technological advancements, i.e., the internet of things (IoT), IPv4 is no more efficiently functioning. Therefore, IPv6 introduced with a novel protocol, i.e., Neighbor Discovery Protocol (NDP). It involves many processes to facilitate the communication operation between nodes (hosts and router) that are located on the same link. NDP does not have any verification mechanism to validate the exchange messages, whether it comes from the legitimate or illegitimate node. Besides, the NDP messages are not secure by its design. Therefore, an attacker may manipulate these messages and perform attacks such as Denial of Service (DoS) attack which is considered a frequent attack that threatens the network of the NDP IPv6 link-local. We have reviewed in this paper the main processes of NDP and the security issues of these processes. In addition, the experiments result shown the NDP processes are completely vulnerable to the DoS attack. Thus, the future direction involves developing a prevention mechanism that aims at securing the NDP processes in the network of IPv6 link-local.