This paper describes the design of a Broadcast Core Network (BCN). The BCN is intended to enable the integration of existing terrestrial broadcast systems into a 5G/6G ecosystem. The existing multimedia content distribution architecture in current broadcast networks and the capabilities of 5G access and core networks (5GC) are analyzed to dissect their limitations. We show, inter alia, how the lack of an equivalent data plane makes it impossible to import a 5GC as a solution. We propose a dynamic model that addresses the necessary structure for integrating a BCN in today’s broadcast networks. The paper then considers the evolution of the BCN up to its integration into a 5G/6G cellular network ecosystem. The required architectural components are described. Detailed definitions of the microservices are included, along with the relationships and message calls to enable relevant use cases. Finally, a simulation and lab prototype were developed to validate the proposal. The lab platform is based on multimedia content broadcasting nodes using ATSC 3.0 and a BCN prototype for its control. The results demonstrate the ability of the proposed solution to maximize spectrum utilization and improve the efficiency of current systems.