nanog mailing list archives

Re: Is it safe to use 240.0.0.0/4


From: "John Levine" <johnl () iecc com>
Date: 18 Jun 2015 02:13:56 -0000

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


Current thread: