For MPLS Layer 3 VPN configuration, it is necessary to use a unique Route Distinguisher (RD) per customer Virtual Routing and Forwarding (VRF) to distinguish the routes of different customers, ensuring their isolation within the shared infrastructure. Additionally, Multiprotocol BGP (MP-BGP) is required for the propagation of customer routes within the provider's backbone, as it supports the carrying of VPNv4 routes which include both the IPv4 prefix and the RD, allowing the VPN routes to be correctly interpreted and routed in the MPLS network.