The smart grid is a complex network that aims to manage the electricity usage and reduce consumption. It is composed of a large number of intelligent devices and systems that exchange sensitive data via several networks (HAN, NAN, FAN). The Neighborhood Area Network covers communications between smart meters and the collector that transmits aggregate data to the control center. The NAN network is vulnerable to several types of attacks (Eavesdropping, spoofing, replay) and, security is essential to protect sensitive information in the NAN. In this paper, we propose to use the IPsec protocol to secure the traffic exchanged between smart meters and the control center. Simulation experiments are conducted to evaluate the latencies for real time NAN applications in urban and rural scenarios.