> Lots of IPv4 p2p links are set up like that.  With IPv6 we have lots more
> address space, so there's less demand for doing it this way, rather than
> burning a prefix just to use for p2p links - but then again, there's
> even more free address space in the last 64 bits than in the first, so
> doing p2p links this way has some advantages.

The scenario should be covered by "Multilink Subnets"
<draft-thaler-ipngwg-multilink-subnets-01.txt>, which is just recently
discussed in ipngwg.  I think it is possible for KAME to implement it
when the technique is well cooked.  But it is apparently not included
in current design of KAME.  It is the reason itojun said that the
configuration should be prohibited for now.

Regards,

Atsushi Onoe