Is it safe to use 240.0.0.0/4

Thu Jun 18 02:34:10 UTC 2015

How many devices need IPs? Is there a reason ARIN can't be used?

Josh Luthman
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On Jun 17, 2015 10:18 PM, "John Levine" <johnl at iecc.com> wrote:

> >IIRC, the short answer why it wasn't repurposed as additional unicast
> >addresses was that too much deployed gear has it hardcoded as
> >"reserved, future functionality unknown, do not use." Following an
> >instruction to repurpose 240/4 as unicast addresses, such gear would
> >not receive new firmware or obsolete out of use quickly enough to be
> >worth the effort.
>
> More to the point, the amount of work required to fix all the existing
> equipment to handle 240/4 would not be a lot less than the work
> required to get it to handle IPv6, and it would only have pushed the
> IPv4 exhaustion out a few years.  It was entirely reasonable to
> conclude that it would not have been a good use of anyone's time or
> money.
>
> Look at the bright side: you can use the money you didn't spend on
> 240/4 upgrades to buy slightly used IPv4 space on the grey market
> or CGN equipment.
>
> R's,
> John
>