HP UX IPv6 Software manual 6to4, Router-to-host tunnel configuration IPv4 host IPv6 host

IP6-in-IP tunnel

IPv4 host

	IPv4 network
IPv4 Router	IPv6/IPv4 Router
IPv6/IPv4 host

Figure 4: router-to-host tunnel configuration

IPv4 host

IPv6 host

IPv6 host

6. 6to4

6to4 is an automatic router-to-router tunneling mechanism that can be used to provide connectivity between isolated IPv6 sites or hosts across the IPv4 infrastructure and with IPv6-only sites via relay routers. Each 6to4 site should have a site border 6to4 (dual stack) router, which is one endpoint of the 6to4 automatic tunnel.

6to4 further defines an address assignment scheme that allows a site to obtain an unique externally routable prefix if the site has at least one globally unique IPv4 address. The Internet Assigned Number Authority has assigned the unique prefix 2002::/16 for 6to4 mechanism. The site border dual stack router should have 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 15.13.136.1, then its 6to4 prefix will be 2002:0f0d:8801::/48. The embedded IPv4 address will be used as the tunnel endpoint address by the 6to4 mechanism.

			IPv6 host
6to4 host
	IPv4 network	6to4 relay router	IPv6 host
6to4 router
6to4 host			IPv6 host
	6to4 router

6to4 host6to4 host

Figure 5: 6to4 network topology

Figure 5 illustrates a 6to4 network topology. 6to4 topology consists of one or more 6to4 hosts in a 6to4 site, a 6to4 border router on the site that has at least one IPv4 connection to the Internet and a 6to4 relay router that is used to connect to native IPv6 site. A 6to4 relay router is different from a 6to4 router in that it has a 6to4 pseudo interface and at least one IPv6 interface.

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