Connecting Ipv6 Islands Across Multiple Ipv4 Domains; Figure 111: Ipv6 Tunneled Across Ipv4 Domains - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - BGP AND MPLS CONFIGURATION GUIDE 2010-10-12 Configuration Manual

JunosE 11.3.x BGP and MPLS Configuration Guide

Connecting IPv6 Islands Across Multiple IPv4 Domains

Figure 111: IPv6 Tunneled Across IPv4 Domains

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Router CE 1 establishes an MP-BGP session over TCPv4 to PE 1 and advertises its ability
to reach the IPv6 network 2001:0430::/32. The MP-BGP update message specifies an
AFI value of 2 (IPv6) and a SAFI value of 1 (unicast). As the next hop in the
MP-REACH-NLRI attribute, CE 1 advertises the IPv6 address of the CE 1 interface that
links to PE 1.
Both IPv4 and IPv6 addresses must be configured on the PE-CE link. The IPv6 address
defaults to an IPv4-compatible address that can be overridden with policy.
PE 1 and PE 2 establish an MP-BGP session using their remote loopback IPv4 addresses
as neighbor addresses. Router PE 1 installs in its IPv6 global routing table the route
advertised by CE 1. MP-BGP on PE 1 then binds a second-level label, L2, and advertises
the route to PE 2 with an AFI value of 2 (IPv6) and a SAFI value of 4 (labeled routes).
The next hop that PE 1 advertises in the MP-REACH-NLRI attribute is the IPv4 address
of its loopback interface, 10.1.1.1, encoded in IPv6 format as ::10.1.1.1.
When MP-BGP on router PE 2 receives the advertisement, it associates the base tunnel
(to 10.1.1.0/24, label L1) with the next hop (::10.1.1.1) that was advertised by PE 1 to reach
the customer IPv6 island, 2001:0430::/32. Router PE 2 then uses MP-BGP (AFI = 2, SAFI
= 1) to advertise to CE 2 its ability to reach this network.
CE 2 sends native IPv6 packets destined for the 2001:0430::/32 network to PE 2. On
receipt, PE 2 performs a lookup in its global IPv6 routing table. PE 2 prepends two labels
to the IPv6 header (L1–L2–IPv6) and then forwards the packet out its core-facing interface
(10.2.2.2).
The P router does a lookup on L1 and label switches the packet toward PE 1. The P router
can either replace L1 with another label or pop L1 if PE 1 requested PHP.
When PE 1 receives the packet on its core-facing interface, it pops all the labels and does
a lookup in the global IPv6 routing table using the destination address in the IPv6 header.
PE 1 then forwards the native IPv6 packet out to CE 1 on the IPv6 link.
When the IPv6 islands are separated by multiple IPv4 domains, the autonomous system
boundary routers between the IPv4 domains must be DS-BGP routers (Figure 111 on
page 480).
Each of these AS boundary routers establishes a peer relationship with the DS-BGP
routers in its own domain, creating a separate mesh of tunnels among the DS-BGP routers
of each domain. Routing between PE 1–ASBR 1 in AS 1 and between PE 2–ASBR 2 in AS
2 is accomplished by means of label-switched paths.
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