H3C Technologies H3C S12500-X Series Switches - Manual (Page 120)

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Figure 37 Network diagram for inter-AS option C
To improve the scalability, you can specify an RR in each AS to maintain all VPN-IPv4 routes and to
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 38 .
Figure 38 Network diagram for inter-AS option C using RRs
Carrier's carrier
If a customer of the MPLS L3VPN service provider is also a service provider, 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 learn the routes of the customer network connected to
a Level 2 carrier. It only learns the routes for delivering packets between different sites of the Level 2
carrier. Routes of the customer networks connected to a Level 2 carrier are exchanged through the BGP
IBGP
IB
G
P
VPN 1
PE 1
PE 3
VPN 1
CE 3
CE 2
VPN 2 VPN 2
PE 4
CE 4
CE 1
AS 100
PE 2
MP
-IBG
P
M
P
-IBGP
ASBR 1
(PE)
RR 1 RR 2
ASBR 2
(PE)
IBGP
IBGP
EBGP
Multi-hop MP-EBGP
VPN LSP
LSP
AS 200
MP
-IB
G
P
M
P-
IBG
P
MPLS backbone MPLS backbone