Juniper BGP, Configuration Manual

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In Figure 81 on page 405, the base tunnels between the PE routers are established in
the IPv4 core networks with LDP or RSVP. The PE routers advertise IPv6 prefixes
from the CE devices within their respective ASs as VPNv6 prefixes with MP-IBGP.
For example, PE 1 advertises the CE 1 prefix 6001:0430::/48 over to PE 2 in its
MP_REACH_NLRI attribute. The next-hop attribute in the update message is the PE
1 loopback address—the IPv4-mapped IPv6 address, FFFF::1.1.1.1/128.
PE 2 advertises 6001:0430::/48 by means of MP-EBGP to PE 3. The prefix is sent as
a VPNv6-labeled prefix (2002:0202/48), with the default BGP next hop being the
IPv4-mapped IPv6 address of the IPv4 interface going to PE 3.
For inter-AS services, in contrast to intra-AS services, JUNOSe software supports both
IPv4 backbone and IPv6 backbone types of BGP next-hop encodings. The default
BGP next-hop encoding used for IPv6 VPN inter-AS services is the one specified for
the IPv4 backbone where IPv4-mapped IPv6 addresses are used. Alternatively, you
might also configure the IPv6 backbone type of BGP next-hop encoding by configuring
route maps that use native IPv6 addresses for the BGP next hop.
Using Route Targets to Configure VPN Topologies
You can use VRF import and export route targets to configure a variety of VPN
topologies, such as full-mesh VPNs, hub-and-spoke VPNs, and overlapping VPNs.
Full-Mesh VPNs
In a full-mesh VPN, each site in the VPN can communicate with every other site in
that same VPN. For example, in Figure 82 on page 406, each site in VPN A can
communicate with all other VPN A sites but not with the sites in VPN B.
Figure 82: Site Connectivity in a Full-Mesh VPN
Figure 83 on page 407 illustrates how you can configure the VRF import and export
route targets to build a full-mesh VPN. Each VRF in VPN A has the same route target,
100:10, in their import list and export list. Each VPN A VRF accepts only received
routes that have this route target attached. Because this route target is attached to
each route advertised by VPN A VRFs, every site in VPN A accepts routes only from
other sites in VPN A. The same principle applies to VPN B.
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Using Route Targets to Configure VPN Topologies
JUNOSe 11.1.x BGP and MPLS Configuration Guide