Overview[1]#

Private-Use Networks is a network that uses private IP Address space, following the standards set by RFC 1918 for Internet Protocol Version 4 (IPv4), and RFC 4193 for Internet Protocol Version 6 (IPv6). These addresses are commonly used for home, office, and enterprise Local Area Networks (LANs).

Private-Use Networks address spaces were originally defined in an effort to delay IPv4 address exhaustion, but they are also a feature of IPv6 where exhaustion is not an issue.

The Internet Engineering Task Force (IETF) has directed the Internet Assigned Numbers Authority (IANA) to reserve the following IPv4 address ranges for private networks, as published in RFC 1918:[1]

RFC 1918 nameIP Address rangenumber of addresseslargest CIDR block (subnet mask)host id sizemask bitsclassful description
24-bit block10.0.0.0 – 10.255.255.25516,777,21610.0.0.0/8 (255.0.0.0)24 bits8 bitssingle class A network
20-bit block172.16.0.0 – 172.31.255.2551,048,576172.16.0.0/12 (255.240.0.0)20 bits12 bits16 contiguous class B networks
16-bit block192.168.0.0 – 192.168.255.25565,536192.168.0.0/16 (255.255.0.0)16 bits16 bits256 contiguous class C networks
N-A100.64.0.1-100.127.255.255100.64.0.0/10100.64.0.0/10 (255.192.0.0)14 bits10 bitsCarrier-grade NAT

Carrier-grade Network Address Translation#

Carrier-grade NAT (CGN) is defined in RFC 6598 allocated 100.64.0.0/10 This address block should not be used either on Private-Use Networks or on the public Internet

it is intended only for use within the internal operations of carrier networks.

Private IPv6 addresses#

Private IPv6 addresses is described in RFC 4193

Private-Use Networks Summary Table#

Address BlockPresent UseReference
0.0.0.0/8"This" NetworkRFC 1122, Section 3.2.1.3
10.0.0.0/8Private-Use NetworksRFC 1918
127.0.0.0/8LoopbackRFC 1122, Section 3.2.1.3
169.254.0.0/16Link LocalRFC 3927
172.16.0.0/12Private-Use NetworksRFC 1918
192.0.0.0/24IETF Protocol AssignmentsRFC 5736
192.0.2.0/24TEST-NET-1RFC 5737
192.88.99.0/246to4 Relay AnycastRFC 3068
192.168.0.0/16Private-Use NetworksRFC 1918
198.18.0.0/15Network Interconnect
Device Benchmark Testing
RFC 2544
198.51.100.0/24TEST-NET-2RFC 5737
203.0.113.0/24TEST-NET-3RFC 5737
224.0.0.0/4MulticastRFC 3171
240.0.0.0/4Reserved for Future UseRFC 1112, Section 4
255.255.255.255/32Limited BroadcastRFC 919, Section 7
RFC 922, Section 7
100.64.0.0/10Carrier-grade NAT (CGN)RFC 6598

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« This page (revision-8) was last changed on 17-Jul-2017 09:12 by jim