HP-UX IPv6 Transport Administrator's Guide for TOUR 1.0

IPv6 Software and Interface Technology
Migrating from IPv4 to IPv6
Chapter 770
Connecting IPv6 Domains over IPv4 Clouds (6to4)
Isolated IPv6 nodes and networks can communicate over an IPv4
network without explicitly configuring tunnels, by using “6to4”
mechanism (RFC 3056). “6to4” effectively uses the IPv4 wide area
network as a unicast point-to-point layer. “6to4” requires no end-node
reconfiguration and minimal router configuration.
“6to4” Well-Known Prefix
The IANA permanently assigned one IPv6 address prefix for “6to4”. It is
2002::/16. The “6to4” prefix 2002:/16 can be prepended to a host or
router’s globally-unique 32-bit IPv4 address (<IPv4-Addr>) to form a
48-bit “6to4” prefix 2002:<IPv4-Addr>. The “6to4” prefix provides a
network prefix for the local IPv6 host or network. The IPv4 address is
the endpoint for all external IPv4 connections.
Figure 7-1 “6to4” Prefix
Encapsulating in IPv4
IPv6 packets from a “6to4” site are encapsulated in IPv4 packets when
they leave the site over its external IPv4 connection. IPv6 packets are
transmitted in IPv4 packets with an IPv4 protocol type of 41, the same
protocol type set when IPv6 packets tunnel inside IPv4 frames according
to RFC 1933.
001 0x002 IPv4 Address SLA ID Interface ID
0 3 16 48 74
127
1.2.3.42002::16
2002:0102:0304::/48