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> There's only 4,294,967,296 addresses in IPv4 In an internet-usable sense, there's fewer than that, too. The entire 127.0.0.0/8 block is for localhost/loopbac
by vacri 11y ago
> There's only 4,294,967,296 addresses in IPv4
In an internet-usable sense, there's fewer than that, too. The entire 127.0.0.0/8 block is for localhost/loopback, for example.
https://en.wikipedia.org/wiki/IPv4#Special-use_addresses https://en.wikipedia.org/wiki/IPv4#Special-use_addresses
- duskwuff 11y agoWorse: 224.0.0.0/4 and 240.0.0.0/4 are reserved, have always been reserved, and cannot in any practical terms be allocated, as there's huge amounts of hardware and software in production that's hard-coded to treat them as invalid. That's 1/8 of the entire IPv4 address space that's completely unusable.
- simoncion 11y ago224.0.0.0/4 is IPv4 multicast space. It's not reserved and often in active use. [0] If there's software that treats IP traffic to or from 240.0.0.0/4 as invalid, then it's defective. I mean, I get that the broken software is a concern, but -if we care about carving out more IPv4 space- it's not something that we should be overly worried about. :) [0] Indeed, mDNS/Bonjour/Avahi uses 224.0.0.251 for service discovery.
- duskwuff 11y agoPerhaps I should clarify: That range isn't general-purpose IP space. And while multicast is useful, there's probably ways to implement it without sacrificing 1/16 of the entire address space.
- simoncion 11y ago> ...while multicast is useful, there's probably ways to implement it without sacrificing 1/16 of the entire address space. It's far too late for that now. :( Perhaps if IPv4 multicast were more widely used on The Internet the large carve-out would look more sensible to you. > That range isn't general-purpose IP space. Yeah, that's a true statement. Just remember that "reserved" has a particular meaning when it comes to IP address ranges. :)