Network automation requires more than configuration deployment: reproducible network validation and operation also depend on an authoritative source of truth, pre-deployment validation, controlled rollout, continuous observability and post-change auditing against configuration drift. However, openly described, self-contained platforms that integrate these functions remain limited. This paper presents a reproducible container-based platform for IP network automation, validation, observability and configuration drift detection, built entirely from open-source components. The architecture integrates Containerlab, FRRouting, NetBox, Ansible, Batfish, LibreNMS and Oxidized within a dual-plane design that separates management and data traffic while funnelling operational access through a dedicated proxy gateway. The resulting environment supports a drift-aware IaC workflow in which the intended state is modelled in a single source of truth, rendered into device configurations, statically validated before deployment, and later compared with the running state through periodic configuration retrieval and diff-based auditing. The platform capabilities are illustrated through representative scenarios covering OSPF behaviour, multi-AS BGP policies and configuration drift detection. These scenarios show that the platform supports realistic routing and operational-consistency analysis under realistic operational constraints while remaining modular, portable, and reproducible.