Inter-AS MPLS L3VPN

This section provides a detailed explanation of MPLS Layer 3 VPN connectivity between different service providers. It focuses on the configuration, verification, and troubleshooting of inter-provider MPLS L3VPN services, helping learners understand how VPN routes and customer traffic can be exchanged across multiple provider networks. Throughout this section, learners will explore Inter-AS MPLS VPN deployment models, including Options A, B, and C. The training explains how each option works, where it is commonly used, and how service providers can choose the right approach based on scalability, operational control, routing design, and security requirements. The section also covers Carrier Supporting Carrier, commonly known as CSC, which allows one service provider to carry another provider’s customer VPN traffic across its MPLS backbone. Learners will understand how CSC supports hierarchical service provider designs and enables scalable connectivity between providers. In addition, this section includes practical guidance on verifying inter-provider MPLS VPN operation and troubleshooting common issues related to route exchange, label distribution, VPN reachability, PE-to-PE communication, and customer traffic forwarding. By the end of this section, learners will have a stronger understanding of how MPLS Layer 3 VPNs are extended between providers using Inter-AS Options A, B, and C, along with Carrier Supporting Carrier designs in real-world service provider environments.