/127 between routers?

[sthaug at nethelp.no]

> In summary, this means that IP stack implementations can't rely on a
> fixed /64 boundary because future standards may come up with new
> address ranges with semantics that require a non-/64 subnet prefix.
> So stack implementations should be coded in a way that supports
> non-/64 prefixes to avoid major rewrites and problems in the future.
> 
> But anything using addresses from the existing ranges may well assume
> a /64 prefix in full compliance with the standards.

Anything assuming only /64 prefixes in the existing ranges would most
likely fail spectacularly given the number non /64 prefixes in use.

For instance, we number our router loopbacks with /128 prefixes from
our global /32. Similarly, our links use /124 prefixes. We have no
intention of changing these to use /64 only.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no