[6bone] semi-newbie Q on IPv6 address planning

[Robert Elz]

    Date:        Fri, 02 Aug 2002 08:43:18 +0900
    From:        itojun@iijlab.net
    Message-ID:  <20020801234318.4D9FA4B22@coconut.itojun.org>

  | 	because "0" is reserved for subnet router anycast address, you shouldn't
  | 	use blah:0/127 for your nodes as unicsat address.  go read the draft
  | 	on this topic.

But you don't need a subnet router anycast address on a p2p link.

If you are a router then ::1 will work just fine to reach the nearest
router...   If you're not, then "the other guy" on the p2p link must
be it (or there is no router at all, in which case it doesn't matter
what address you use).

It can't be used from outside the link, as there's no way for outside nodes
to discover the 'n' that applies to  the figure at the top of page 14 of
the draft (if you configure that on some node, you may as well just
configure the router address - anycast or unicast - that it would reach).
[Aside: do notice that 'n' is used, not "64"]

Unless someone can come up with some kind of technical reason why every
subnet in the universe must be forced to use a /64 prefix, people are just
going to go on using whatever they like.   And "the doc says" is not a
technical reason (nor does the doc contain one).   No question, if the
prefix length is > 64 then autoconfiguration isn't going to work, but on
p2p links (and some eothers) that's usually irrelevant, and in any case,
whether autoconfig gets used is always for the local site to decide.

kre