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C HAPTERS UPPLEMENT

9

This online supplement of Chapter 9 gives you a brief overview of how to deploy 6VPE acro

more than one autonomous system that is running MPLS. You can deploy 6VPE over multip

autonomous systems in the same way as described in Chapter 7, MPLS VPN: Inter-

Autonomous MPLS VPN or Carriers Carrier.

Inter-Autonomous Systems 6VPE

Spanning the 6VPE solution across multiple autonomous systems is specified in RFC 4364. Yo

can use three methods that are discussed in Chapter 7 to provide inter-as support for 6VPE:

Virtual routing/forwarding (VRF)-to-VRF connections between autonomous system (A

border routers

MP-eBGP exchanging vpnv6 prefixes + label between AS border routers

MP-eBGP exchanging vpnv6 prefixes + label between PE routers or route reflectors (RR

and exchanging IPv4 prefixes + label for the PE IPv4/32 prefixes

In the first option, you can have AS border routers (ASBR) from different autonomous system

exchange the IPv6 prefixes directly over VRF interfaces. The two ASBRs must have one link

common between them for each VPN for which they are exchanging prefixes. These links ca

be (sub)interfaces with vrf forwardingconfigured on them. The packets that cross the links

between the two ASBRs are unlabeled IPv6 packets. The second option is to have ASBRs fro

different autonomous systems exchange vpnv6 prefixes and labels. The packets that cross th

links between the ASBRs are labeled packets. The third option is to have the vpnv6 prefixes an

labels exchanged between PE routers or RRs from different autonomous systems. However,

labeled IPv4 path needs to exist between the PE routers or RRs from the different autonomosystems. Therefore, an IPv4 prefixes + label exchange must take place between the ASBRs f

the PE IPv4/32 prefixes. These PE IPv4/32 prefixes + label can be advertised via MP-eBGP

via an Interior Gateway Protocol (IGP) and Label Distribution Protocol (LDP). If the RRs fro

different autonomous systems exchange the vpnv6 prefixes, they must leave the BGP next-ho

field unchanged.

IPv6 over MPLS

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733 Chapter 9: IPv6 over MPLS

Carriers Carrier Through 6VPE

Because LDP for IPv6 is not available, Carriers Carrier (CsC) for IPv6 is a bit different from

for IPv4. You learned from Chapter 7 that CsC involves sending labeled packets over a VRF

interface of the PE router. The same is true for CsC for IPv6. Two scenarios are possible for

transporting IPv6 with a CsC solution:

6VPE over IPv4 MPLS network

CsC network is MPLS VPN for IPv4

In the first scenario, 6VPE over IPv4 MPLS network, you have a regular 6VPE network run

over an IPv4 MPLS backbone. The IPv6 packets switched between the PE and CE routers are

labeled. Because LDP for IPv6 is not available, the only option is to run MP-eBGP for IPv6 + l

between the PE and CE routers. You do this by configuring the send-labelkeyword for the eB

neighbor on the PE and CE router. Figure 9-1 shows the CsC 6VPE over IPv4 MPLS networ

scenario in a schematic form.

Figure 9-1 6VPE over IPv4 MPLS Network

The second scenario, CsC network is MPLS VPN for IPv4, is a regular CsC MPLS VPN for

IPv4 network, meaning that the CsC is running MPLS VPN for IPv4 with IPv4 prefixes + laexchange between the CsC PE and the carriers CE routers. The carrier network is running M

IPv4 end to end in its network and has 6VPE configured on the PEs only. The PE IPv4/32 pre

are the prefixes from the carriers network that must be labeled. On the PE routers of the carr

network is MP-eBGP for IPv6 + label configured toward the CE routers to carry the custom

prefixes. Figure 9-2 shows the second scenario in a schematic form.

CsC-PECsC-PE

IPv4 MPLS Backbone

MPLS for IPv4MP-eBGP for IPv6

+ Label

VPN Red

Site

1

Site

2

VPN Red

VRF VRF

MP-eBGP for IPv6+ Label

MP-iBGP for vpnv6 + Label

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Carriers Carrier Through 6VPE

Figure 9-2 CsC Network Is MPLS VPN for IPv4

NOTE To better understand the operation of CsC, refer to the section Carriers Carrier

Chapter 7.

VPN Red VPN Red

Carrier Network Site 1

CustomerNetwork

Site 1

CustoNetwo

Site

Carrier Network Site 2MPLS VPN for IPv4 Network

Carriers Carrier Network

MP-eBGP for

IPv6 + Label

VRF VRF

CE CEPE CsC-PE CsC-PE

VRF VRF

IPv4 + Label IPv4 + Label

MPLS VPN for IPv4

MP-eBGP for

IPv6 + Label

MP-iBGP for vpnv6 + Label

PE