> I'm a bit confused about the difference between a 6to4 router and a
> 6to4 relay router.
> I understand that a 6to4 routers are used between 6to4 sites, while
> 6to4 relay routers are used between native IPv6 sites and 6to4 sites.
> However, what exactly is a 6to4 site and a native IPv6 site? Don't
> both type of routers forward IPv6 packets over IPv4 networks, which
> means both routers work in a IPv6 network? Or does the difference only
> lies in the IP addresses used, i.e. 6to4 routers accept only 6to4
> source and destination addresses (2002::/16 prefixes) and 6to4 relay
> routers accept only 6to4 source/native IPv6 dest (2001::/16 prefixes)
> addresses and native IPv6 source/6to4 dest addresses? If that's the
> case, why have the distinction? Why not just use 6to4 routers?
> Also, looking at the diagram in
> what is a IPv6 island? Is it a private IPv6 network setup by say,
> organizations and schools?
An IPv6 "island" is an IPv6 network adrift in an IPv4 "sea." To talk to
other "islands" or the IPv6 Internet, somehow IPv6 traffic needs to be
tunneled through the IPv4 network. 6to4 is one of those ways to tunnel.
BTW, all of 2000::/3 is the global unicast range, not just 2001::/16.
For example, www.ipv6tf.org you mention has IPv6 address
2a01:48:1:0:2e0:81ff:fe05:4658. (Although it doesn't seem to answer.
Maybe someone fat-fingered the DNS entry?)
A 6to4 router encapsulates/decapsulates IPv6-in-IPv4 traffic between an
IPv6 site (without IPv6 native connectivity) and the IPv4 Internet for
transport to/from another IPv6 router (hence another IPv6 site without
native connectivity) or, more likely, an IPv6 relay router (for
transport to native IPv6 sites). The IPv4 side has a public IP address
from the site's assigned IPv4 range.
An organization could also use 6to4 routers to interconnect IPv6 islands
within its intranet with no concern for connectivity to other
organizations or the IPv6 Internet.
An IPv6 relay router encapsulates/decapsulates IPv6-in-IPv4 traffic
between the IPv6 Internet and the IPv4 Internet. The IPv4 side has the
anycast address 220.127.116.11 (but theoretically any address in
18.104.22.168/24), and the IPv6 side advertises routes to 2002::/16 (i.e.,
6to4 routers on the IPv4 Internet).