Making Use of 240/4 NetBlock

Joe Maimon jmaimon at
Sun Mar 13 21:14:43 UTC 2022

Christopher Morrow wrote:
> On Sun, Mar 13, 2022 at 10:39 AM William Herrin <bill at 
> <mailto:bill at>> wrote:
>     On Sun, Mar 13, 2022 at 1:22 AM Joe Maimon <jmaimon at
>     <mailto:jmaimon at>> wrote:
>     > The true dilemma is that any amelioration of IPv4 scarcity may
>     indeed
>     > contribute to further delaying mass global IPv6 adoption,
>     regardless of
>     > whose effort and time is involved.
> What's the actual proposal for 240/4?
> Is it: "Make this usable by me on my /intranet/?"
> Is it: "Make this usable across the internet between bespoke endpoints?"
> Is it: "Make this usable for any services/users on the wider internet, 
> treat it like any other unicast ipv4 address?"
> Is it: "Something entirely different"
> The first 2 probably already work today, if you take the time to 
> control the horizontal and vertical of your networking space.
> The last is probably workable, given enough time to flush out all of 
> the endpoints which (today) probably treat 240/4 as 'special'.

240/4 has a special problem. The problem is that the smallest bit of 
cooperation from the broader community, other than those expending 
effort on 240/4 directly is required.

Mostly so that any potential use of 240/4 continues to be standardized. 
Which in theory, is in all parties best interest.

I think the current draft pretty much wanted a word or two changed.

> So.. to move forward with 240/4 on the wider internet you'd need a 
> bunch of software / hardware updates, and time for those to rollout.
> Then you'd need sacrificial lambs in the user and service endpoints.

Nobody is asking for any assistance with that. It will happen or not 
based upon those who wish to expend effort on it. Apparently, most if it 
has already happened.

> All of this to regain ~16 /8's worth of space (presuming you could use 
> 255/8?).

Really, so that anything standardized can be done with it, rather than 

This is about extending some utilization capability of IPv4, but it is 
also about preserving standard driven behavior.

> I think a /8 is 'free' on the internet for about a month, so 1.5 yrs 
> of new address allocations, terrific?

That was the old paradigm, in the old days. Currently a /8 goes pretty 
far and its likely to only get further.

> At the end of the day, again, almost all proposals to 'add more ipv4 
> space' come down to 1 month per /8.
> I think part of Jordi's point is:
>   "Is that 1 month really worth the effort?

All the effort requested is for all those who think its wall head 
banging to say knock yourself out, we are unopposed to changing how IPv4 
obsolete addresses are managed because we have already bet on IPv6. Take 
whatever you want. Change whatever you want. We dont care.

Thats not a whole lot of effort being requested of the unwilling in 
exchange for their continued relevance. All the rest of the efforts are 
expected to come from the willing, able and ready. Not your concern.

But perhaps you do care. Why?

>   is there a reason that all of the softare/hardware uplift and time 
> to deploy is not being spent on v6?"

Perhaps you think that stymieing any effort on IPv4 is important to 
marshall the worlds attention to IPv6. Which if the shoe were on the 
other foot you would find galling and obnoxious.

There are many reasons why IPv6 hasnt done that all on its own and 
pretty much most if not all of them have nothing to do with 240/4

They have to do with IPv6. And we have heard them over and over again. 
Look inwards.

In short, IPv6 apparently keep losing to the cost vs. benefits analysis 
being performed by countless people in countless situations. You can 
claim that it should not, but that is not what is happening.

You cant make IPv4 more expensive than it already is doing all by 
itself. It is wrong to try. And apparently, its not expensive enough to 
drive mass adoption of v6, with any degree of alacrity.

v6 must have costs in contexts that have been under-addressed. Its time 
to knowledge them and perhaps work to address them.

> At this point in our matrix timeline it seems to me that:
>   "If you were going to deploy v6, you did... if you didn't oh, well.. 
> eventually you will?"

Much like Itanium vs. amd64, there are other ways this can turn out, the 
longer it drags out. I think those ways are potentially more undesirable 
than extending IPv4 use in a standardized fashion now.

> I'd prefer to not have to deploy  in a rush or on timelines I can't 
> cointrol if I hadn't deployed already.
> Will that timeline be 'soon' anytime soon? I don't know :( I think 
> Grant's "not until i'm long retired" guess
> is as good as any though :(
> -chris

I for one would like to say I did all the tiny amount I conceivably 
could to leave the internet a better place than I found it.

And I think that means giving IPv4 all the runway it needs to properly 
decelerate to the fullest extent possible or at least not obstructing 
those who would try.

Remember, the dual stack migration was predicated on working v4. They 
are just trying to patch that flawed transition plan to keep it going.

Its really hard to explain to people how 4bn IPv4 addresses are all used 
up while at the same time there are still more than a hundred million of 
addresses in theory potentially available but unusable by anybody. 
Without pointing fingers. Especially when its the same people who have 
just paid some significant sum for the rights to use a few of those numbers.


More information about the NANOG mailing list