Making Use of 240/4 NetBlock

David Conrad drc at
Wed Mar 9 19:34:21 UTC 2022


On Mar 9, 2022, at 10:45 AM, John Levine <johnl at> wrote:
>> When did squatting become a justification for not allocating addresses?
> Um, when can I register my .corp and .home domains?

Um, are you suggesting there is sufficiently heavy use of 240/4 to result in a significant security/stability issue if the address space is allocated?  I thought you were arguing too many systems would have to be updated to even send/receive packets with 240/4 in the source or destination field.

You’re equating the use of address space explicitly reserved “for future use” (or for multicast use) with unallocated name space. A more reasonable (but still flawed) analogy to .corp and .home would be the squatting on 1/8. I was at IANA when we allocated 1/8 to APNIC and recall the gnashing of teeth that resulted. Yet we have a demonstration proof that 1/8 could be made usable.

I don’t really have a dog in this fight and my intuition suggests that trying to make 240/4 global unicast wouldn’t be worth the effort, but I remain of the belief that it would be better to have actual data on what breaks if there was an attempt to use it than to come up with specious arguments like “but it might annoy squatters”.


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