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Comment by ggm | Hacker News Reader

Makes sense. Also 240.0.0.0/4. small focussed change in code. getting the IANA process worked out with the IAB is going to take a bit more work. (from the experience with 240/4 where I tried with some others to author a draft)

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While at it, I feel like we could also squeeze the 224.0.0.0–239.255.255.255 multicast range to maybe 224.0.0.0/8 if not tighter.

For reference here is a list of reserved ipv4 addresses[0].

[0] https://en.m.wikipedia.org/wiki/Reserved_IP_addresses

This would break a ton of existing applications

This can't be done, there's a number of devices out there that do multicast on fixed multicast IPs and so doing this would break them. In particular I've got a series of HDMI<=>IP devices that forcefully go to 239.255.42.[42..141] depending on their settings.

I wonder, though, how many of those fixed multicast IPs are outside of both 224/8 and 239/8.

225/8-231/8 were reserved for future multicast use and never allocated by iana. As near as we can tell by grepping the entire world's source they are entirely unused.

128m addresses....

yea that'd probably be reasonable to try to reclaim then. probably only useful for private use unfortunately though, i bet there's a lot of stuff that'll improperly route them given the range.

We've had 225/8-231/8 up and running for 6+ months, with patches for various routing daemons. Running a gauntlet with 240/4 and 0/8 now working seemed best.

In our exploration of converting these 120m addresses from a multicast definition to unicast, we only had to change the kernel with two tiny patches, and recompile 89 fedora packages. Openwrt was less. The patches for frr and bird, straightforward.

As for private or public use, certainly there is demand for a larger CGNAT address space, somewhere, and allocation of a portion of 225-231 for that might drive adoption there.

Still, the addresses need to become routable, and from there (aside from politics and depoloyment delay), globally routable is the dream for most of these new addresses, in 5-10 years.

or you could just move to fucking v6, its not that hard.

Yes this 240/4 is the one range I wish they would allow, even if just for private ranges. The main showstopper is Windows iirc, as Linux already allows it (will route it).

What are some resources to help support this concept move along?

Drop myself and the other project members a line and see the unicast extensions project on github.

It is a trivial number of patches to enable all the open source code in the world to work.

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