Some advice on IPv6 planning and ARIN request, please

Radu-Adrian Feurdean nanog at
Sat Jul 8 21:00:33 CST 2017

On Sat, Jul 8, 2017, at 19:13, Mel Beckman wrote:
> Radu,
> Are you assuming that a goal of IPv6 is to efficiently fill subsets? I

No, but I assume IPv6 is still subject to common-sense.

> among them easy mapping of MAC addresses for transition purposes and the
> security that discourages malefactors from quickly enumerating active
> devices in a subnet.

I do get all those points. And by the way, try to explain the same to
security people.

> But that's not the main reason for /64 basic subsets. One of the guiding
> principles of IPv6 was to not make the mistake of underestimating the
> future applications of IP addresses. Thus your question "what hotel room

... so it went directly to over-estimating ....

> has 65536 items in it?" has no meaning in terms of future applications.
> As you point out, we're not talking about hotel rooms. We don't, by
> definition, know what we're talking about for future applications.

All this by forgetting today's applications.
And no, you can't possibly treat the same way a hotel room and a 4 floor
site with a server room.

> I tell people in my IPv6 classes that we have to stop thinking of
> ourselves in a spacesuit with a limited air supply that must be rationed,
> and instead recognize that we're now in a wide-open planet-sized
> atmosphere where we can breathe freely, and without apportionment. 

Well, by having 64 bits for each subnet, I start lacking bits for other
things (like inter-devices connections, ....). I'm not in a space-suit,
but I'm on top of Kilimanjaro, where air pressure is only half of what
we're used to.

> That open atmosphere was by design. It's why IPv6 uses 128-bit addresses,

That's for hosts. When you care more about subnets, it's shortened to 64

> They're just integers. Not lumps of gold. 

Be careful, IPv4 got upgraded from numbers to gold a number of years

> And there's more where those came from :)

Hopefully. I'm just curious if 8000::/4 will obey today's rules or not.

Back to the original question, I find it delirious to treat a small
entity the same as a big one, especially when the size difference
between the two is several orders of magnitude. Even if we consider
"future applications", there's still a very high chance that the size
will still matter. Get "the IT guy" of a small company to get used with
a /48 for his 20 people, 5 printers and 2-3 servers set-up,  then
imagine what happens with a design of a "site" 10 or 100 times bigger.
This is something that you already see with VLAN ids and RFC1918 space.
Even if you think you gave people "as much as they will ever need", they
will still end up needing more.

More information about the NANOG mailing list