IPv6 RPL (Protocol for Low Power and Lossy Networks) was designed as a proactive protocol to achieve reliable routing in IoT (Internet of Things) scenarios with high efficiency. However, most of the intrinsic security features make it vulnerable to numerous routing attacks, which seriously threaten the performance and reliability in IoT networks. Such weaknesses surely have to be addressed, considering that IoT systems are increasingly permeating critical sectors such as healthcare, smart cities, and industrial automation. Hence, this research was triggered by the increasing demand of security in IoTs’ networks from such types of threats to ensure secure and reliable operation of interconnected systems. The key focus of this work is to perform modeling-based safety risk analysis in the RPL protocol, considering attack scenarios and their impacts on critical performance indices, including energy consumption, radio consumption, packet loss, and stability in the network. This paper follows a strict methodology and relies on the Contiki/Cooja simulator to create scenarios for the purpose of gaining valuable insight into how IoT networks act under an attack. Accordingly, five types of attacks, such as DIS flooding, Black Hole, and Version Number, have been emulated to present their influence on network resources. In contrast, these results reflect a huge deterioration in network performance, with energy consumption, radio communication overhead, and packet loss increasing massively in attack conditions. From these results, one important detection approach along with mitigation methods becomes very crucial to face different vulnerabilities of RPL effectively. Gained knowledge will help develop better security mechanisms for protection against newly arising threats in IoT networks.