HP MSR1002-4 Configuration Manual page 199

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Multihop EBGP redistribution of labeled VPN-IPv4 routes between PE routers—PEs
advertise VPN-IPv4 routes to each other through MP-EBGP. This solution is also called
inter-AS option C.
For more information about the three inter-AS VPN solutions, see "Configuring MPLS L3VPN."
Based on these solutions, there are three ways to implement inter-AS MD VPN:
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MD VPN inter-AS option A
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MD VPN inter-AS option B
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MD VPN inter-AS option C
MD VPN inter-AS option A
As shown in
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Two VPN instances are in AS 1 and AS 2.
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PE 3 and PE 4 are ASBRs for AS 1 and AS 2, respectively.
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PE 3 and PE 4 are interconnected through their respective VPN instance and treat each other
as a CE device.
Figure 67 MD VPN inter-AS option A
Public instance
CE 1
VPN instance 1
To implement MD VPN inter-AS option A, a separate MD must be created in each AS. Multicast data
is transmitted between the VPNs in different ASs through the MDs.
Multicast packets of VPN instance 1 are delivered as follows:
1. CE 1 forwards the multicast packet of VPN instance 1 to PE 1.
2. PE 1 encapsulates the multicast packet into a public network packet and forwards it to PE 3
through the MTI interface in MD 1.
3. PE 3 considers PE 4 as a CE device of VPN instance 1, so PE 3 forwards the multicast packet
to PE 4.
4. PE 4 considers PE 3 as a CE device of VPN instance 2, so it forwards the multicast packet to
PE 2 through the MTI interface in MD 2 on the public network.
5. PE 2 forwards the multicast packet to CE 2.
Because only VPN multicast data is forwarded between ASBRs, different PIM modes can run within
different ASs. However, the same PIM mode must run on all interfaces that belong to the same VPN
(including interfaces with VPN bindings on ASBRs).
MD VPN inter-AS option B
In MD VPN inter-AS option B, RPF vector and BGP connector are introduced:
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RPF vector—Attribute encapsulated in a PIM join message. It is the next hop of BGP MDT route
from the local PE device to the remote PE device. Typically, it is the ASBR in the local AS.
Figure 67:
PE 1' P 1
AS 1
MTI 1
MTI 1
PE 1"
MT 1
MD 1
VPN instance-VPN instance
ASBR ASBR
PE 3' PE 4' P 2
AS 2
MTI 2
PE 4"
PE 3"
MT 2
MD 2
VPN instance 2
190
PE 2'
MTI 2
CE 2
PE 2"