A VPN service provider can have customers that are themselves VPN service providers. In this type of configuration, also called a hierarchical or recursive VPN, the customer VPN service provider’s VPN-IPv4 routes are considered external routes, and the backbone VPN service provider does not import them into its VRF table. The backbone VPN service provider imports only the customer VPN service provider’s internal routes into its VRF table.
This type of configuration is similar to the configuration described in the Internet Service Provider as the Customer section. The similarities and differences are shown in Table 14.
Table 14: Comparison of Interprovider and Carrier-of-Carriers VPNs