The performance evaluation of network protocols in high-density networks could be a challenge issue due to the large number of nodes which dealing with actual testbeds. Thus, simulations are usually used. This paper presents a simulation study results for RPL protocol in high-density networks. Two objective functions were used, namely: the Objective Function Zero (OF0) and the Minimum Rank with Hysteresis Objective Function (MRHOF)). Grid topology is studied, and three performance metrics were used: Packet Delivery Ratio (PDR), Power Consumption, and Number of hops (Hop Count). The evaluation and comparison of the two objective functions are based on three parameters: number of nodes, successful reception ratio (RX) and network topology. The results of the simulation disclose that these parameters have a significant effect on the PDR, consumed power, and the Hop Count. The results show that the RPL performance can provide a better performance for OF0 that MRHOF could not provide.