The extension of Layer 3 Virtual Private Network (L3VPN) services over a FlexVPN framework with an internet best-effort underlay transport was explored in this study. The integration of FlexVPN, known for its scalability and flexibility, with internet-based underlay transport aimed to provide a cost-effective and efficient solution for deploying multiple L3VPN services. A detailed network architecture analysis focused on performance metrics such as latency, throughput, and packet loss under varying traffic conditions. The results indicated that while the best-effort underlay transport introduces variability in performance, the FlexVPN framework effectively mitigates these effects, maintaining acceptable service levels. This study demonstrates the feasibility of leveraging FlexVPN with internet best-effort underlay for L3VPN services, offering valuable insights for network designers seeking to optimize VPN deployments in cost-sensitive environments.