Carrier's Carrier - HP MSR2000 Configuration Manual

The public tunnel from PE 3 to ASBR 2 is set up. The next hop for the route to PE 1 is ASBR 2. The
incoming label for the public tunnel on ASBR 2 is L3, and the outgoing label is L2.
6. Within AS 200, the public tunnel from PE 3 to ASBR 2 is required to be set up hop by hop through
a label distribution protocol, for example, LDP.
MPLS packets cannot be forwarded directly from PE 3 to ASBR 2. Assume that the outgoing label
for the public tunnel on PE 3 is Lv.
After route advertisement and public tunnel setup, a packet is forwarded from CE 3 to CE 1 by using the
following process:
7. PE 3 performs the following routing table lookups for the packet:
a. Finds a matching route with next hop PE 1 and inner label Lx, and encapsulates the packet with
label Lx.
b. Finds the route to PE 1 with next hop ASBR 2 and label L3, and encapsulates the packet with
label L3 as the outer label.
c. Finds the route to ASBR 2 with outgoing label Lv, and encapsulates the packet with label Lv as
the outmost label.
8. AS 200 transmits the packet to ASBR 2 by the outmost label.
9. ASBR 2 removes the outmost label, replaces L3 with L2, and forwards the packet to ASBR 1.
10. ASBR 1 replaces L2 with L1, and forwards the packet.
11. AS 100 transmits the packet to PE 1 by the outer label.
12. PE 1 removes the outer label, and forwards the packet to CE 1 according to the inner label Lx.
As shown in
routes with PEs in the same AS. The RR in each AS maintains all VPN-IPv4 routes. The RRs in two ASs
establish a multihop MP-EBGP session to advertise VPN-IPv4 routes.
Figure 49 Network diagram for inter-AS option C using RRs
VPN 1
CE 1
MPLS backbone
AS 100
CE 2
VPN 2

Carrier's carrier

If a customer of an MPLS L3VPN service provider is also a service provider:
The MPLS L3VPN service provider is called the provider carrier or the Level 1 carrier.
•
Figure 49, to improve scalability, you can specify an RR in each AS to exchange VPN-IPv4
PE 1
ASBR 1
RR 1
IBGP
PE 2
Multi-hop MP-EBGP
ASBR 2
(PE) (PE)
RR 2
EBGP
IBGP
VPN LSP
LSP
176
VPN 1
CE 3
PE 3
MPLS backbone
AS 200
PE 4
CE 4
Private LSP
Public LSP
VPN 2