For a Carrier Supporting Carrier (CSC) VPRN where the customer carrier is a BGP/MPLS VPN...

The customer carrier network can be a pure IP network.

The customer carrier can provide Layer 2 and Layer 3 services to its end-customers.

If the customer carrier offers VPRN services, PE routers residing in different customer carrier sites must run iBGP between them to exchange IPv4 routes.

If the customer carrier offers VPRN services, the network provider stores the end-customer routes in its CSC VPRN.