draft-schoen-intarea-unicast-240-06.txt   draft-schoen-intarea-unicast-240-07.txt 
Internet Engineering Task Force S.D. Schoen Internet Engineering Task Force S.D. Schoen
Internet-Draft J. Gilmore Internet-Draft J. Gilmore
Updates: 1122, 3704, 6890 (if approved) D. Täht Updates: 1122, 3704, 6890 (if approved) D. Täht
Intended status: Standards Track IPv4 Unicast Extensions Project Intended status: Standards Track IPv4 Unicast Extensions Project
Expires: 1 July 2024 29 December 2023 Expires: 30 December 2024 28 June 2024
Unicast Use of the Formerly Reserved 240/4 Unicast Use of the Formerly Reserved 240/4
draft-schoen-intarea-unicast-240-06 draft-schoen-intarea-unicast-240-07
Abstract Abstract
This document redesignates 240/4, the region of the IPv4 address This document redesignates 240/4, the region of the IPv4 address
space historically known as "Experimental," "Future Use," or "Class space historically known as "Experimental," "Future Use," or "Class
E" address space, so that this space is no longer reserved. It asks E" address space, so that this space is no longer reserved. It asks
implementers to make addresses in this range fully usable for unicast implementers to make addresses in this range fully usable for unicast
use on the Internet. use on the Internet.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on 1 July 2024. This Internet-Draft will expire on 30 December 2024.
Copyright Notice Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License. provided without warranty as described in the Revised BSD License.
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6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6.1. Existing Unofficial Uses of 240/4 . . . . . . . . . . . . 11 6.1. Existing Unofficial Uses of 240/4 . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . 13 8.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Implementation Status . . . . . . . . . . . . . . . 16 Appendix A. Implementation Status . . . . . . . . . . . . . . . 16
A.1. Operating systems . . . . . . . . . . . . . . . . . . . . 16 A.1. Operating systems . . . . . . . . . . . . . . . . . . . . 16
A.2. Routers and Switches . . . . . . . . . . . . . . . . . . 17 A.2. Routers and Switches . . . . . . . . . . . . . . . . . . 17
A.3. DHCP implementations . . . . . . . . . . . . . . . . . . 18 A.3. DHCP implementations . . . . . . . . . . . . . . . . . . 18
A.4. Other implementations . . . . . . . . . . . . . . . . . . 18 A.4. Other implementations . . . . . . . . . . . . . . . . . . 19
A.5. Internet of Things . . . . . . . . . . . . . . . . . . . 18 A.5. Internet of Things . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
With ever-increasing pressure to conserve IP address space on the With ever-increasing pressure to conserve IP address space on the
Internet, it makes sense to consider where relatively minor changes Internet, it makes sense to consider where relatively minor changes
can be made to fielded practice to improve numbering efficiency. One can be made to fielded practice to improve numbering efficiency. One
such change, proposed by this document, is to redefine the such change, proposed by this document, is to redefine the
"Experimental" or "Future Use" 240/4 region (historically known as "Experimental" or "Future Use" 240/4 region (historically known as
"Class E" addresses) as ordinary unicast addresses. These 268 "Class E" addresses) as ordinary unicast addresses. These 268
million IPv4 addresses are already usable for unicast traffic in many million IPv4 addresses are already usable for unicast traffic in many
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Operators of networks that are making unofficial uses of portions of Operators of networks that are making unofficial uses of portions of
240/4 may wish to plan to discontinue these uses and renumber their 240/4 may wish to plan to discontinue these uses and renumber their
internal networks, or to request that IANA formally designate certain internal networks, or to request that IANA formally designate certain
ranges as additional Private-Use areas. ranges as additional Private-Use areas.
7. Acknowledgements 7. Acknowledgements
This document directly builds on prior work by Dave Täht and John This document directly builds on prior work by Dave Täht and John
Gilmore as part of the IPv4 Unicast Extensions Project. Gilmore as part of the IPv4 Unicast Extensions Project.
We thank our late colleague Michael J. Karels (1956-2024) for his
comments on this draft and related FreeBSD implementation efforts.
8. References 8. References
8.1. Normative References 8.1. Normative References
[IANA4] Internet Assigned Numbers Authority, "IANA IPv4 Special- [IANA4] Internet Assigned Numbers Authority, "IANA IPv4 Special-
Purpose Address Registry", Purpose Address Registry",
<https://www.iana.org/assignments/iana-ipv4-special- <https://www.iana.org/assignments/iana-ipv4-special-
registry/iana-ipv4-special-registry.xhtml>. registry/iana-ipv4-special-registry.xhtml>.
[RFC0870] Reynolds, J. and J. Postel, "Assigned numbers", RFC 870, [RFC0870] Reynolds, J. and J. Postel, "Assigned numbers", RFC 870,
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ipv4#ipv4_routable_240.0.0.0_4>. ipv4#ipv4_routable_240.0.0.0_4>.
[Atlas] RIPE Network Coordination Centre, "RIPE Atlas", [Atlas] RIPE Network Coordination Centre, "RIPE Atlas",
<https://atlas.ripe.net/>. <https://atlas.ripe.net/>.
[Cloudflare] [Cloudflare]
Strong, M., "Fixing reachability to 1.1.1.1, GLOBALLY!", 4 Strong, M., "Fixing reachability to 1.1.1.1, GLOBALLY!", 4
April 2018, <https://blog.cloudflare.com/fixing- April 2018, <https://blog.cloudflare.com/fixing-
reachability-to-1-1-1-1-globally/>. reachability-to-1-1-1-1-globally/>.
[Cox] Cartwright-Cox, B. and Z. Pospíchal, "On "Reclaiming"
240.0.0.0/4", 23 May 2024,
<https://ripe88.ripe.net/archives/video/1367/>.
[Dale] Dale, L. and F. Korsbäck, "Dive Deep on AWS Networking [Dale] Dale, L. and F. Korsbäck, "Dive Deep on AWS Networking
Infrastructure (presentation)", NANOG88, June 2023, Infrastructure (presentation)", NANOG88, June 2023,
<https://www.youtube.com/watch?v=0tcR-iQce7s&t=1709s>. <https://www.youtube.com/watch?v=0tcR-iQce7s&t=1709s>.
[FLM] Fuller, V., Lear, E., and D. Meyer, "Reclassifying 240/4 [FLM] Fuller, V., Lear, E., and D. Meyer, "Reclassifying 240/4
as usable unicast address space", Work in Progress, as usable unicast address space", Work in Progress,
Internet-Draft, draft-fuller-240space-02, 25 March 2008, Internet-Draft, draft-fuller-240space-02, 25 March 2008,
<https://datatracker.ietf.org/doc/html/draft-fuller- <https://datatracker.ietf.org/doc/html/draft-fuller-
240space-02>. 240space-02>.
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We have prepared a patch which enables 240/4 support this on NetBSD. We have prepared a patch which enables 240/4 support this on NetBSD.
It has not been merged as of December 2023. It has not been merged as of December 2023.
240/4 traffic is blocked by default in all versions of the Microsoft 240/4 traffic is blocked by default in all versions of the Microsoft
Windows operating system. Windows will not assign an interface Windows operating system. Windows will not assign an interface
address in this range, if one is offered by DHCP. address in this range, if one is offered by DHCP.
A.2. Routers and Switches A.2. Routers and Switches
Unless otherwise noted, support in this section reflects interface
assignment and packet-forwarding support, not BGP support, which may
involve separate bogon logic.
240/4 has been tested to interoperate as ordinary unicast in 2019 in 240/4 has been tested to interoperate as ordinary unicast in 2019 in
a Cisco router using IOS release 6.5.2.28I, which was also released a Cisco router using IOS release-XR 6.5.2.28I, which was also
in 2019. Older and newer releases are also likely to work. released in 2019. Older and newer releases are also likely to work.
Cisco also has two other router OS variants which have not been
tested.
240/4 traffic is blocked by default in Juniper's router operating 240/4 traffic is blocked by default in Juniper's router operating
system, but can be enabled with a simple configuration switch, system, but can be enabled with a simple configuration switch,
starting from the JUNOS 9.6 release in June 2010. See page 50 of starting from the JUNOS 9.6 release in June 2010. See page 50 of
[JUNOS-release-notes-9.6]. It notes, "The JUNOS Software now allows [JUNOS-release-notes-9.6]. It notes, "The JUNOS Software now allows
Class E addresses to be configured on interfaces. To allow Class E Class E addresses to be configured on interfaces. To allow Class E
addresses to be configured on interfaces, remove the Class E prefix addresses to be configured on interfaces, remove the Class E prefix
from the list of martian addresses by including the [edit routing- from the list of martian addresses by including the [edit routing-
options martians 240/4 orlonger allow] configuration statement." See options martians 240/4 orlonger allow] configuration statement." See
also chapter 5, "Martian Addresses" on page 129 through 136 of the also chapter 5, "Martian Addresses" on page 129 through 136 of the
2022 documentation [JUNOS-routing-properties]. It includes a 2022 documentation [JUNOS-routing-properties]. It includes a
completely worked example on "Removing the Class E Prefix on Martian completely worked example on "Removing the Class E Prefix on Martian
Addresses". Addresses".
Arista switches running EOS 4.25.2F (from February 2021), and later Arista switches running EOS 4.25.2F (from February 2021), and later
releases, include the command "ipv4 routable 240.0.0.0/4" which releases, include the command "ipv4 routable 240.0.0.0/4" which
enables the use of 240/4 addresses on interfaces and in packet enables the use of 240/4 addresses on interfaces and in packet
routing. The default is to disable this ability. routing. The default is to disable this ability.
[Arista-user-manual] [Arista-user-manual]
The Belkin AX3200 router (with firmware 1.0.01 build 101415 Oct 14, The Belkin AX3200 router (with firmware 1.0.01 build 101415 Oct 14,
2020) cannot use addresses from 240/4 locally, but is happy to route 2020) cannot use addresses from 240/4 locally, but is happy to route
packets to such addresses elsewhere in the Internet. packets to such addresses elsewhere in the Internet.
A 2024 presentation by Ben Cartwright-Cox [Cox] reported on his
experiments on support for 240/4 in several router environments
(including BGP). According to Cartwright-Cox, RouterOS 7.7 and IOS
XR fully support 240/4. Arista(v)EOS 4.29.0.2F allows opting in to
240/4 support and is believed to work when this is enabled, although
it could not be fully tested in Cartwright-Cox's virtualized
environment. JunOS 22.X similarly allows opting in to 240/4 support,
and can properly use and route addresses in this range statically and
dynamically, although its built-in DHCP server is not willing to
assign them to other devices on a locally attached network. Finally,
EXOS 31.1.1.6-1, IOS XE, Nokia SR-OS, and Huawei VRP generally did
not support using or routing 240/4, while the latter three exhibited
an apparent bug in which they would ostensibly accept dynamic routes
within 240/4 but not actually apply these into the RIB or FIB.
A.3. DHCP implementations A.3. DHCP implementations
Support for 240/4 addressing may be typical of many DHCP Support for 240/4 addressing may be typical of many DHCP
implementations (because the 240/4 address assignment special case implementations (because the 240/4 address assignment special case
has often been handled at the kernel level). If the underlying has often been handled at the kernel level). If the underlying
operating system supports 240/4 assignment to an interface, the final operating system supports 240/4 assignment to an interface, the final
official ISC DHCP release (4.4.3) supports 240/4 allocation as both official ISC DHCP release (4.4.3) supports 240/4 allocation as both
client and server, as do Busybox DHCP udhcpc/udhcpd (release 1.1.15), client and server, as do Busybox DHCP udhcpc/udhcpd (release 1.1.15),
and ISC Kea (which currently includes only a DHCP server and ISC Kea (which currently includes only a DHCP server
implementation). implementation).
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