In this paper, we present a reference multi-layer hierarchical network topology that spans from access to core networks, specifically designed to meet the demands of next-generation 6G communication systems. This topology, inspired by the actual network deployments of Telefónica in medium-sized countries in Europe and America, integrates both IP and optical (DWDM) layers to provide a comprehensive framework for network design, optimization, and analysis. Our primary contribution is the development of an open-source benchmarking network, accessible to both researchers and industry professionals. This resource aims to facilitate the study and advancement of integrated IP and optical networks, addressing key challenges such as traffic aggregation, latency reduction, cost efficiency, and support for advancedapplications. We provide guidelines for utilizing this benchmark network, enabling users to evaluate and enhance their solutions for AI-driven network management, ultra-reliable low-latency communication, enhanced mobile broadband, and massive machine-type communication. By sharing this detailed and practical benchmarking network, we seek to foster innovation and collaboration within the optical network community, driving forward the capabilities and performance of future communication networks.