Question about 6to4

Ted Mittelstaedt tedm at
Thu May 14 23:32:11 CEST 2009

Hi All,

 I apologize in advance if this has been asked before a million times but
I have what is probably a stupid question about 6to4.

 We are in process of connecting to native IPv6, I am currently getting
the IPv6 BGP table from our upstream.

  I see that Linksys is supporting IPv6 out-of-the-box in some of it's
routers, via 6to4

  I figured this might be useful for some of our customers, to setup
a 6to4 relay router for these Linksys devices to use.  I have found plenty
of info on the Internet to setup a router as a 6to4 relay.

  My question concerns how exactly 6to4 -works-

  My understanding is that RFC3068 defines 2002:c058:6301:: as the
anycast for the (in this case) customer router to find the 6to4 relay I
create.  And that a 6to4 relay then uses a manufactured 2002:: IPv6
address formed by using it's IPv4 address with the 2002:: prefix, and
that any 6to4 routers tunneled into it are using their manufactured
2002:xxxx:: addresses.

  So, if this is the case then wouldn't every 6to4 relay that's advertising
on the Intenet be present in the IPv6 BGP table?

  In looking at the various IPv6 looking glasses on the Internet, I see
a handful of 2002:: routes out there.

  But there seems to be no consistency anywhere.  Most of the looking
seem to show Hurricaine Electric's 2002:: advertisement, including my
own table.

  But beyond that, the advertisements for other relays seem to exist in
one router, but not in others.

  Advertisements for native routes do seem to be consistent.

  How exactly do routers know where to forward IPv6 packets destined for
a given 6to4   2002:: address if there is no route in their table?  And if
they are just sending 6to4 traffic to HE then how does HE know what to
do with it if it's not for their network?


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