LoRaWAN is amongst the most prominent LPWAN (Low Power Wide Area Networking) technologies and provides an operation mode, called Class B, where devices can be reached with limited latency. One of the most important features of LoRaWAN Class B is multicast, which allows a single transmission to be shared by multiple multicast group member end-devices. This enables key IoT functionalities such as FOTA (Firmware Over The Air) and other applications that need to transfer multiple packets to a set of end-devices. This thesis will delve into LoRaWAN Class B multicast and study its scalability -- the most important behavior to study in all IoT technologies. An ns-3 module for LoRaWAN Class B multicast has been extended and used for in-depth analysis and drawing scalability insights. The study also explores methods to improve performance as well as enhance scalability.