Which mechanism makes identical customer-private routes unique when advertised in VRF-based VPNs?

The Route Distinguisher (RD) is an 8-byte value prepended to customer IPv4 prefixes, creating a unique 96-bit VPNv4 address. This ensures that identical IP prefixes from different customers, or even from the same customer in different VRFs, are treated as distinct routes within the MPLS VPN backbone. Without the RD, the provider edge (PE) router would see duplicate routes and discard all but one. Route Targets (RTs) are used for controlling the import and export of routes between VRFs, not for making them unique. MP-BGP is the routing protocol used to exchange VPNv4 routes, but it's the RD that provides the uniqueness. LDP is used for label distribution, unrelated to route uniqueness in this context.