Special Use IPv4 Addresses
Internet Corporation for Assigned Names and Numbers
12025 Waterfront Drive, Suite 30090094-2536Los Angeles, CAUnited States of America+310-823-9358michelle.cotton@icann.org
http://www.icann.org/
Internet Corporation for Assigned Names and Numbers
12025 Waterfront Drive, Suite 30090094-2536Los Angeles, CAUnited States of America+310-823-9358leo.vegoda@icann.org
http://www.icann.org/
specialaddressesipv4
This document describes the global and other specialized IPv4 address
blocks that have been assigned by the Internet Assigned Numbers Authority
(IANA). It does not address IPv4 address space assigned to operators and
users through the Regional Internet Registries, nor does it address IPv4
address space assigned directly by IANA prior to the creation of the Regional
Internet Registries. It also does not address allocations or assignments of
IPv6 addresses or autonomous system numbers. This document obsoletes RFC 5735
and updates RFC 6441.
The substantive change between this document and RFC 5735 is that it includes
100.64.0.0/10, which was assigned in RFC 6598.
Throughout its history, the Internet has employed a
central Internet Assigned Numbers Authority (IANA) responsible
for the allocation and assignment of various identifiers needed
for the operation of the Internet . In the
case of the IPv4 address space, the IANA allocates parts of the
address space to Regional Internet Registries (RIRs) according to their
established needs. These RIRs are responsible for the registration
of IPv4 addresses to operators and users of the Internet within
their regions.
On an ongoing basis, IANA assignmnets have been made using policies
established by the IETF to support the Internet Standards Process
described in Section 4 of .
Small portions of the IPv4 address space have been allocated or
assigned directly by the IANA for global or other specialized
purposes. These allocations and assignments have been
documented in a variety of RFCs and other documents. This
document is intended to collect these scattered references and
provide a current list of special use IPv4 addresses.
This document is a revision of RFC 5735 , which it
obsoletes; its primary purpose is to reflect the changes to the list of special
IPv4 assignments since the publication of RFC 5735. It is a companion to
which describes special IPv6 addresses.
0.0.0.0/8 - Addresses in this block refer to source hosts on "this"
network. Address 0.0.0.0/32 may be used as a source address for
this host on this network; other addresses within 0.0.0.0/8 may be
used to refer to specified hosts on this network , section 3.2.1.3.
10.0.0.0/8 - This block is set aside for use in
private networks. Its intended use is documented
in . As described in that
RFC, addresses within this block do not legitimately appear
on the public Internet. These addresses can be used
without any coordination with IANA or an Internet
registry.
127.0.0.0/8 - This block is assigned for use as the
Internet host loopback address. A datagram sent by
a higher level protocol to an address anywhere
within this block loops back inside the host.
This is ordinarily implemented using only
127.0.0.1/32 for loopback. As described in
, Section 3.2.1.3,
addresses within the entire 127.0.0.0/8 block do
not legitimately appear on any network anywhere.
100.64.0.0/10 - This block is used as Shared Address Space.
states that Shared Address
Space can only be used in Service Provider networks or on routing
equipment that is able to do address translation across router
interfaces when addresses are identical on two different interfaces.
169.254.0.0/16 - This is the "link local" block. As described in
, it is allocated for communication between hosts
on a single link. Hosts obtain these addresses by auto-configuration, such
as when a DHCP server cannot be found.
172.16.0.0/12 - This block is set aside for use in
private networks. Its intended use is documented
in . As described in that
RFC, addresses within this block do not legitimately appear
the public Internet. These addresses can be used
without any coordination with IANA or an Internet
registry.
192.0.0.0/24 - This block is reserved for IETF protocol assignments.
At the time of writing this document, there are no current assignments.
Allocation policy for future assignments is given in .
192.0.2.0/24 - This block is assigned as
"TEST-NET-1" for use in documentation and example
code. It is often used in conjunction with domain
names example.com or example.net in vendor and
protocol documentation. As described in
, addresses within this
block do not legitimately appear on the public Internet and can
be used without any coordination with IANA or an
Internet registry. See .
192.88.99.0/24 - This block is allocated for use as
6to4 relay anycast addresses, in to
. In contrast with previously
described blocks, packets destined to addresses from
this block do appear in the public
Internet. , Section 7
describes operational practices to prevent the
malicious use of this block in routing protocols.
192.168.0.0/16 - This block is set aside for use in
private networks. Its intended use is documented in
. As described in that
RFC, addresses within this block do not legitimately appear
the public Internet. These addresses can be used
without any coordination with IANA or an Internet
registry.
198.18.0.0/15 - This block has been allocated for use in benchmark
tests of network interconnect devices. explains
that this range was assigned to minimize the chance of conflict in case a
testing device were to be accidentally connected to part of the Internet.
Packets with source addresses from this range are not meant to be
forwarded across the Internet.
198.51.100.0/24 - This block is assigned as
"TEST-NET-2" for use in documentation and example
code. It is often used in conjunction with domain
names example.com or example.net in vendor and
protocol documentation. As described in
, addresses within this
block do not legitimately appear on the public Internet and can
be used without any coordination with IANA or an
Internet registry.
203.0.113.0/24 - This block is assigned as
"TEST-NET-3" for use in documentation and example
code. It is often used in conjunction with domain
names example.com or example.net in vendor and
protocol documentation. As described in
, addresses within this
block do not legitimately appear on the public Internet and can
be used without any coordination with IANA or an
Internet registry.
224.0.0.0/4 - This block, formerly known as the Class D address
space, is allocated for use in IPv4 multicast address assignments.
The IANA guidelines for assignments from this space are described in
.
240.0.0.0/4 - This block, formerly known as the
Class E address space, is reserved for future use,
see , section 4.
The one exception to this is the "limited
broadcast" destination address 255.255.255.255. As
described in and
, packets with this
destination address are not forwarded at IP layer.
Address Block Present Use Reference
------------------------------------------------------------------
0.0.0.0/8 "This" Network RFC 1122, sect 3.2.1.3
10.0.0.0/8 Private-Use Networks RFC 1918
100.64.0.0/10 Shared Address Space RFC 6598
127.0.0.0/8 Loopback RFC 1122, sect 3.2.1.3
169.254.0.0/16 Link Local RFC 3927
172.16.0.0/12 Private-Use Networks RFC 1918
192.0.0.0/24 IETF Protocol Assignments RFC 5736
192.0.2.0/24 TEST-NET-1 RFC 5737
192.88.99.0/24 6to4 Relay Anycast RFC 3068
192.168.0.0/16 Private-Use Networks RFC 1918
198.18.0.0/15 Network Interconnect
Device Benchmark Testing RFC 2544
198.51.100.0/24 TEST-NET-2 RFC 5737
203.0.113.0/24 TEST-NET-3 RFC 5737
224.0.0.0/4 Multicast RFC 5771
240.0.0.0/4 Reserved for Future Use RFC 1112, sect 4
255.255.255.255/32 Limited Broadcast RFC 919, sect 7
This document describes the past and current practices, but does not create any new
requirements for assignments or allocations by the IANA.
The particular assigned values of special use IPv4 addresses
cataloged in this document do not directly raise security issues.
However, the Internet does not inherently protect against abuse of
these addresses; if you expect (for instance) that all packets from
a private address space such as the 10.0.0.0/8 block or the link
local block 169.254.0.0/16 originate within your subnet, all
routers at the border of your network should filter such packets
that originate from outside your network. Attacks have been mounted
that depend on the unexpected use of some of these addresses.
It should also be noted that some of these address blocks may be used
legitimately outside of a single administrative domain, and may appear
on the global Internet. Security policy should not blindly filter all
of these address spaces without due consideration, and network operators
are encouraged to review this document, and references contained therein,
and determine what security policies should be associated with each of
these address blocks within their specific operating environments.
Many people have made comments on draft versions of this document.
The authors would especially like to thank Scott Bradner, Randy Bush,
Harald Alvestrand, Peter Koch, Alfred Hoenes, and Jari Arkko for
their constructive feedback and comments. They would also like to
offer a special note of thanks to APNIC, which nominated
198.51.100.0/24 and 203.0.113.0/24.