Is it safe to use 240.0.0.0/4

Thu Jun 18 02:13:56 UTC 2015

>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