Redesignation of 240/4 from "Future Use" to "Limited Use for Large Private Internets"
Asia Pacific Network Information
Centre
pwilson@apnic.net
http://www.apnic.net
Asia Pacific Network Information
Centre
ggm@apnic.net
http://www.apnic.net
Asia Pacific Network Information
Centre
gih@apnic.net
http://www.apnic.net
Internet Area
Individual Submission
This document directs the IANA to designate the block of IPv4
addresses from 240.0.0.0 to 255.255.255.255 (240.0.0.0/4) as
unicast address space for limited use in large private
Internets.
The address block spanning 240.0.0.0 to 255.255.255.255
(240.0.0.0/4), formerly designated as "Class E", and noted as
being "Reserved" in the IANA IPv4 address registry, is
no longer to be held in reserve by IANA for the IETF.
IANA is directed to redesignate the address block 240.0.0.0/4
as unicast address space intended for private use in large
private Internets that require more address space than is
available in the private use address space designated by .
Potential users of this address space need to ensure
that their envisaged deployment can satisfy the use caveats
noted here.
Many implementations of the TCP/IP protocol stack have the
240.0.0.0/4 address block marked as experimental, and prevent
the host from forwarding IP packets with addresses drawn from
this address block.
For this reason, it is strongly suggested that private
network addressing requirements which can be fulfilled from the
private use address space designated by should continue to use that space.
Network administrators with very large scale requirements for
private use address space who wish to use addresses drawn from
240.0.0.0/4 are advised to conduct appropriate tests to ensure
that such addresses can be used in their envisaged private use
context.
[Note: not for publication. It is suggested that in order to
assist with verification of equipment compatibility, a separate
informational RFC or other mechanism be developed to assist with
the recording of specific test results, upgrade status, etc.]
Equipment deployed on the public Internet is configured by
default to treat addresses in the block 240.0.0.0/4 as
experimental addresses that cannot be forwarded. This implies
that accidental leakage of packets destined to such addresses
would conventionally be discarded.
The IANA is directed to redesignate the block of IPv4
addresses from 240.0.0.0 to 255.255.255.255 as unicast address
space reserved for "Limited Use for Large Private
Internets".
The authors would like to acknowledge the thoughtful assistance
of David Conrad, Andy Davidson and Robert Seastrom in the
preparation of this document.