The amount of data transferred in a smart grid system, and its reliability impose to add new communication technologies to the power line communication network using the electricity infrastructure. RPL, a well-known routing protocol in smart grid application, has been specially designed to support the constraints of low power and lossy networks. In this paper we propose to study the impact of combining a radio and a PLC interface in a smart metering architecture, by modifying RPL to handle both available interface. Using discrete event simulation, we show how the network can be more resilient to failure while the overall quality of service can be significantly increased.