The CMS is one of the four detectors at the Large Hadron Collider (LHC). As it´s name suggest, one of it´s central characteristics is the detection of muons. The Muon Spectrometer of the CMS uses three different technologies: Resistive Plate Chambers (RPCs), Drift Tubes (DTs), and Cathode Strip Chambers (CSCs). During the Phase II upgrade for the HL-LHC the RPCs system will be extended to the forward region 1.6 < | η | < 2.4 to increase redundancy and to enhance the trigger and reconstruction capabilities. In order to provide the expected performance of the different proposed technologies, simulation of the new geometry, event generation, digitization and validation of this implementations are on going. This talk present the process to implement the new digitization and its validation.