3Com MSR 50 Series Configuration Manual page 1472

1472 C 79: MPLS L3VPN C
HAPTER ONFIGURATION
When every AS needs to exchange a great amount of VPN routes, the ASBRs may
become bottlenecks hindering network extension.
One way to solve the above problem is to make PEs directly exchange VPN-IPv4
routes without the participation of ASBRs:
Two ASBRs advertise labeled IPv4 routes to PEs in their respective ASs through
■
MP-IBGP.
The ASBRs neither maintain VPN-IPv4 routes nor advertise VPN-IPv4 routes to
■
each other.
An ASBR maintains labeled IPv4 routes of the PEs in the AS and advertises them
■
to the peers in the other ASs. The ASBR of another AS also advertises labeled
IPv4 routes. Thus, an LSP is established between the ingress PE and egress PE.
Between PEs of different ASs, Multi-hop EBGP connections are established to
■
exchange VPN-IPv4 routes.
Figure 415 Network diagram for inter-provider VPN option C
VPN 1
CE 1
PE 1
MPLS backbone
AS 100
PE 2
CE 1
VPN 2
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-provider VPNv4 connection to advertise VPN-IPv4 routes, as
shown in Figure 416.
Multi-hop MP-EBGP
ASBR 2
ASBR 1
(PE)
(PE) EBGP
Multi-hop MP-EBGP
VPN LSP
LSP
VPN 1
CE 3
PE 3
MPLS backbone
AS 200
PE 4
CE 4
VPN 2