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There are several proposals. The most current one merely advocates that 240/4 be moved from reserved for future use to unicast status, which is the deployed reality today.

I hate the idea of wasting 6% of the original internet on rfc1918 space.

Given it is already used internally, it cannot be used as public space. The only practical option for it is RFC1918.

If people are using space that has been marked as "Reserved For Future Use" within their networks, then this is a problem that they must deal with and it must not affect or influence global usage. What about networks squatting on DoD /8 space? Does this mean the DoD can never route this space publicly because people are using it internally?

DoD space /8 is different as it is within the public space of IPv4, even if it was never advertised globally.

Whereas 240/4 was never declared public.

Apples and Oranges.

You are correct, 240/4 was never marked as public space, it was marked as Reserved for Future Use. Network operators squatting on 240/4 space should have never done so as it was not decided as to what it was going to be used for, hence its current status.

Like I said, if people squat on reserved space and the status changes, that's too bad for them if it's reallocated and made routable. Network operators have no right to dictate that space cannot be made routable, simply because they are using space internally and against current policies.

> If Windows was changed to allow it at that point, today hardly anyone would be complaining that Ciscos or Junipers or other core routers don’t support it.

Yes. But it wasn’t. Making this proposal a day late and a dollar short.

Well, I would put a dollar on this proposal being made again and again over the years to come. It’s still not too late.

Why do we need more RFC1918 addresses? What's wrong with 10.0.0.0/8?

Some larger companies need it. I say if their equipment supports it and it's currently unused globally, then let it work internally.

Fair enough.

This proposal is not regarding repurposing 240/4 as RFC1918 space. It is regarding reclassifying it as Unicast space. I would recommend reading the article.

My bad. I was replying to the parent comment but you're right that I should have read the article.

> So for a quick win, Windows just needs to drop special checks they do for 240/4.

Notging special because it's actually in the routing table, as it should be.

Issue ROUTE PRINT to see it yourself.

Haven’t checked in a couple years, but can you assign a 240.0.0.1/24 for example to the local NIC on Windows?

Assigning is another deal (tested on 2012R2):

    netsh interface ipv4>add add "4084" 200.0.0.1 255.255.255.0

    netsh interface ipv4>add add "4084" 240.0.0.1 255.255.255.0
    The parameter is incorrect.

    netsh interface ipv4>sh add 4084

    Configuration for interface "4084"
        DHCP enabled:                         No
        IP Address:                           200.0.0.1
        Subnet Prefix:                        200.0.0.0/24 (mask 255.255.255.0)
        InterfaceMetric:                      10

The GUI interface explicitly tells to use 'from 1 to 223' for the first octet.

Our proposal isn't for 240/4 to be reclassified as RFC1918 space, it's for it to be reclassified as unicast space.

If its just about internal networks then just use a nonrouteable IP. Its not like there are a shortage addresses in the 10.0.0.0/8 network. That is almost 17 million addresses you can do anything with. Somehow if you do run out then just add an extra router and suddenly you have another almost 17 million addresses.

"just add an extra router".

I think when conceiving of potential issues with this, or thinking about the possible problems of trying to merge two overlapping networks together, your imagination is coming up a little short.

It's never that simple.

The networks could not overlap if the given range does not route. Anyways, that misses the point as the challenges of configuring the corresponding routing table would be trivial compared to managing 16 million devices on a single internal network.

I’ve worked with large organisations that have merged dozens of companies networks. There were lots of clashes.

I’ve also worked with companies where their networks filled up almost all the 10/8 space and they were running out of room. Having to do things like shrink subnets at individual locations and deal with issues around not able to install all the equipment they originally wanted. It’s a real pain.

And yes, the entire 10/8 space needed to be routable through to the corporate support desk, SIEM tools, payment systems, loyalty systems, security and other IoT systems, etc.

Yes sure you could probably NAT things, or switch to tools/approaches that don’t require every device to have an internally routable IP, but then that’s a terrible argument akin to arguments against IPv6.