IPv6 represents an incomprehensibly large space. [...] Divided
evenly, this could allow every person on the planet to control 14
million networks, so why be frugal?
Because it's not about just the numbers. If it were, there'd be no
IPv4 space crunch at all, rather than the minor one we have now.
Like v4, v6 space is managed hierarchically, both in assignment and, in
a different way, routing. There is no surer way to run out of a finite
resource than to think of, and treat, it as infinite. We did that with
v4. We did that with our planet's ability to supply us with petroleum.
We did that with our planet's ability to absorb and detoxify the
various wastes we generate. And, guess what? We're coming up against
the finiteness of these "infinite" resources. Treat v6 the same way
and the same thing will happen.
The lower 64 bits, the v6 interface,
There really is no such thing. One relatively common way to assign v6
addresses is to use a /64 with an EUI64 in the low 64 bits, but it's
hardly the only way, and there definitely is no reason to assume
everyone will do it. (There are also reasons to not do it; it's
extremely annoying to swap network cards, or move the disk to another
machine, and have the machine silently change addresses on you.)
Of course, if a DNSL decides that it will list at /64 granularity,
that's its business. Some v4 DNSLs are coarser than /32, too. But
anything that has the assumption that every /64 can be treated as
homogenous wired into it will have a rather nasty awakening when it
runs up against reality.
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