/127 between routers?

[Matsuzaki Yoshinobu]

Jim Burwell <jimb at jsbc.cc> wrote
> Makes sense to me.  It would seem to me that /126s were always the
> logical equivalents of /30s in the IPv4 world for use on p-t-p links. 
> /127s always seemed "wrong"  to me, since it uses the "magic" all-zeros
> network identifier address as a host address.  :p 
> 
> When I first started learning about IPv6, I wondered it the all-zeros or
> all-ones host chunk of an IPv6 address held any special meaning as they
> do in IPv4, and quickly figured out that all-ones doesn't, but all-zeros
> still does.  A bit annoying in some ways since /127 would make a nice
> XYZ::0,1 p-t-p interface address pairs, but oh well.  /126 it is.

In case of /126s on p-to-p links, there is an unused all-ones address.
I still worry about it.
 - http://archive.apnic.net/meetings/26/program/apops/matsuzaki-ipv6-p2p.pdf

A vendor said me the cost of special care for these unused address is
too high - you need double lookup to prevent packet loops.  And they
decided not to perform such double lookup.  So I prefer /127s on
p-to-p links.  It's like an operational insurance to prevent packet
loops.
-----
Matsuzaki Yoshinobu <maz at iij.ad.jp>
 - IIJ/AS2497  INOC-DBA: 2497*629