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I am confused with the uniqueness of Route Distinguisher and Route Target in an MPLS L3VPN network
Are they unique for each VPN within separate Provider Edge (PE), meaning different PE could use the same value? Or are they unique for each VPN across the whole MPLS network (in all PE)?
The Route Distinguisher would be unique within the MPLS VRF across the MPLS network. In regard to IPv4 the RD is an 8 byte value which is combined with an 4 byte IPv4 address to create a unique VPNv4 address/prefix that is carried through the MPLS network. Each PE would see the same RD for a given VPNv4 address/prefix.
The Route Target is more a mechanism to control the VPNv4. As an example, you could use the Route Target to allow only specific PE/CEs on a given MPLS VRF to learn specific VPNv4 Addresses/prefixes.
