Carrier-of-Carriers Using BGP as the Label Distribution Protocol
You can run BGP instead of LDP as the label distribution protocol on the PE-CE link
between the Tier 1 and the Tier 2 carriers in a carrier-of-carriers topology. This
capability is available for carriers providing Internet access or VPN service to end
users.
Carrier-of-Carriers IPv6 VPNs
Figure 109 on page 475 illustrates a carrier-of-carrier scenario with IPv6 VPNs. MPLS
labels are exchanged on the PE–CE link for customer-internal routes, but
customer-external routes are not imported either into the VRFs on the PE router or
into the core. VRFs maintain a routing table only for the customer-internal routes.
Forwarding is accomplished primarily by label switching, without a routing table
lookup.
Only customer-external routes (Tier 2 ISP routes as shown in Figure 109 on page 475)
can be native IPv6 addresses. Because LDP over TCP over IPv6 is not currently
supported, the customer-internal routes for which LDP can give out labels (Tier 1 ISP
routes in Figure 109 on page 475) must be IPv4 addresses; they cannot be IPv6
addresses, whether native or IPv4-mapped.
For more information about carrier-of-carriers VPNs, see “Carrier-of-Carriers IPv4
VPNs” on page 469 .
Figure 109: Carrier-of-Carrier IPv6 VPNs
Carrier-of-Carriers IPv6 VPNs ■ 475
Chapter 5: Configuring BGP-MPLS Applications
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