202
Figure 55
Network diagram for inter-AS option C
To improve the scalability, you can specify an RR in each AS, making it maintain all VPN-IPv4 routes and
exchange VPN-IPv4 routes with PEs in the AS. The RRs in two ASs establish an inter-AS VPNv4
connection to advertise VPN-IPv4 routes, as shown in
.
Figure 56
Network diagram for inter-AS option C using RRs
Carrier’s carrier
Introduction to carrier's carrier
It is possible that a customer of the MPLS L3VPN service provider is also a service provider. In this case,
the MPLS L3VPN service provider is called the provider carrier or the Level 1 carrier, while the customer
is called the customer carrier or the Level 2 carrier. This networking model is referred to as carrier’s carrier.
In this model, the Level 2 service provider serves as a CE of the Level 1 service provider.
For good scalability, the Level 1 carrier does not redistribute the routes of the customer network
connected to a Level 2 carrier; it only redistributes the routes for delivering packets between different sites
