Some advice on IPv6 planning and ARIN request, please

Mel Beckman mel at
Sat Jul 8 17:13:15 CST 2017


Are you assuming that a goal of IPv6 is to efficiently fill subsets? I submit that it is not. There are advantages to sparse address spaces, among them easy mapping of MAC addresses for transition purposes and the security that discourages malefactors from quickly enumerating active devices in a subnet.

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 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.

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. 

That open atmosphere was by design. It's why IPv6 uses 128-bit addresses, and not 48- or 64-bit. In the exponential space of integers, IPv6 selected a maximum integer that was many orders of magnitude greater than we could ever imagine needing at the time.

They're just integers. Not lumps of gold. And there's more where those came from :)

 -mel beckman

> On Jul 8, 2017, at 10:00 AM, Radu-Adrian Feurdean <nanog at> wrote:
>> On Sat, Jul 8, 2017, at 03:06, Owen DeLong wrote:
>> consider a /48 per guest room as well as a /48 per hotel for the hotel
>> itself.
> I think the classfull madness of "/48 everywhere" should stop at some
> point; the "every subnet is a /64" is enough already.
> A /48 is 65536 *subnets*, with each subnet having space for what can be
> considered "unlimited" number of devices.
> A /56 already is 256 *subnets*. 
> Now please show be a hotel room that has close to 65536 items in it
> (also tell me how much does a night in such a room cost).
> Then how many rooms may host close to 256 devices that can transmit and
> receive data ?
> And then again, at the end of the day a hotel is *NOT* and ISP, a hotel
> is a hotel. Internet access is just an extra service that became
> mandatory lately in order to remain "competitive".

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