Very Computer

Hi,

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
http://www.ipv6tf.org/index.php?page=using/connectivity/6to4
what is a IPv6 island? Is it a private IPv6 network setup by say,
organizations and schools?

Thank you.

Regards,
Rayne

Hi Rayne

Islands / Clouds are Private networks not directly attached to the
internet i.e. the network inside of a company for example.

 From some research there is not so much difference between the two
types of routers, relay routers take the full IPv6 address and route
that across the Internet or IPv4 network, where as routers will only
deal with the /16 addresses.

An IPv6 to 4 network is where all machines on that network follow 6to4
rules and cannot have addresses outside of /16.

Regards Mike

So why set up a 6to4 site over a native IPv6 site? Do I get the 6to4
2002::/16 prefix because my ISP doesn't support IPv6 yet and so I'm
unable to get a 2001::/16 prefix (which I understand would make my
site part of a native IPv6 site). So the only way I can communicate
with other IPv6 sites is using the 6to4 scheme over the IPv4 network.

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 192.88.99.1 (but theoretically any address in
192.88.99.0/24), and the IPv6 side advertises routes to 2002::/16 (i.e.,
6to4 routers on the IPv4 Internet).