Hi, > As we see ISPs and community would like to have more IPv4 space in use. > > I would like to ask a question what do people think about other side of > IPv4 numeration space. Because we have in IPv4 a lot of addresses not in > use at all but that space could be easy used. > > 240.0.0.0/4 Reserved (former Class E network) RFC 1700
I remember people looking into that years ago, and the conclusion was that in too many routers and operating systems the 240/4 block was hard-coded as unusable. I just checked the Linux source code and that restriction was removed there around 2008, but similar code was present in so many different places that it wasn't a viable solution. Remember that it wouldn't just be the organisation getting a block from 240/4, it would also affect everybody trying to communicate with them. Operating systems refusing to connect to a 240/4 address would make any website hosted on a 240/4 address badly reachable. Same for DNS servers hosted on such an address etc. > it's 16 */8 networks. More then 256 Millions of routable and never used > IPv4. That is actually not that much. In 2012 when we ran out of free IPv4 space for normal use the rate of allocation world-wide was more than a /8 per month. Even if we could use 240/4 these days, it would probably last us a year or so, and then we would be back where we are today. So in short: - 240/4 use is problematic - software needs to be changed in many places to make it usable - same for configurations (bogon filters etc) - it wouldn't last us much longer than a year anyway - we still need to move to IPv6 because we will have again run out Even shorter: we would use up 240/4 in less time than we would need to make it actually usable, so let's not. If we are changing stuff let's just spend our energy on implementing IPv6 instead. Cheers, Sander
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