HP-UX IPv6 Transport Administrator Guide HP-UX 11i v3 (5992-6426, May 2013)

NOTE: Refer to the ifconfig(1m) man page and the
/etc/rc.config.d/netfconf-ipv6 file for more detailed information on tunneling
parameters.
“6to4” - Connecting IPv6 Domains over IPv4 Clouds
“6to4” is an automatic tunneling mechanism that can be used to provide connectivity
between isolated IPv6 domains or hosts across an IPv4 infrastructure and with native
IPv6 domains via relay routers. “6to4” is based on the IP6-in-IP tunneling mechanism
defined in RFC 2893 and it falls under the router-to-router tunneling scenario.
“6to4” uses the concept of automatic tunneling where the tunnel end-point is determined
from the IPv6 destination address and avoids the complexity of manual tunnel
configuration. It does not use the IPv4-compatible address, but instead determines the
tunnel endpoint IPv4 address from the special “6to4” prefix of the IPv6 destination
address.
“6to4” Well-Known Prefix
“6to4” defines an address assignment scheme that allows a site to obtain a unique
externally routable prefix if the site has at least one globally unique IPv4 address. The
Internet Assigned Number Authority (IANA) has assigned the unique IPv6 address prefix
of 2002::/16 for “6to4”. Each site must have a border dual stack router that has at
least one global IPv4 address.
A “6to4” prefix can be generated by concatenating the 2002:: prefix to the global
IPv4 address. For example, if the dual stack router has an IPv4 address 15.1.1.1, then
its “6to4” prefix will be 2002:0f01:0101::/48. 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 12 “6to4” Prefix
“6to4” Encapsulation
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
Migrating from IPv4 to IPv6 59