Can anyone write a little bit on 240.0.0.0/4 ("Future use"), 48.0.0.0/8 ("Prudential securities", same as Wachovia?) and 25.0.0.0/8, what they are about and why they're seemingly entirely unused?
240/4 ("class E") addresses were intended a buffer for future allocation, but they can't use it for global unicast because a lot of equipment considers any IP above 239.255.255.255 to be invalid. There have been RFCs to make it formally global-unicast and local-unicast but none have succeeded because of the above-mentionned poorly programmed equipment.
That said, if you know your equipment can handle it like some network operators know theirs can, there is nothing stopping you from using it as a /4 local address space.
"That said, if you know your equipment can handle it like some network operators know theirs can, there is nothing stopping you from using it as a /4 local address space."
Though that would just exarcerbate the problem by producing yet more resistance against allowing that gigantic network to become useful public space.
There have been multiple attempts at making 240/4 globally useful. It pretty much just works on most gear today (except windows), but the resistance by the IPv6 crowd to opening up 1/16th of the ipv4 internet for general use, astounding. There have been multiple internet drafts that did not make it through the relevant committees. Example: https://www.ietf.org/id/draft-schoen-intarea-unicast-240-03....
This makes it sound as if the ipv6 crowd would be larger than "the windows crowd". Perhaps start with convincing every windows user first, then "the ipv6 crowd" should be easily convinced.
