Private-use IPv4 consists of three blocks: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. IPv6 has a distinct local-use category called Unique-Local Address (ULA), with the prefix fc00::/7. These are separate classifications; the IPv4 ranges do not apply to IPv6.
What are the private IPv4 address ranges?
IANA classifies the three IPv4 blocks below as Private-Use under RFC 1918. The endpoint ranges are included to make the boundaries clear.
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| IPv4 CIDR block | Address range |
|---|---|
| 10.0.0.0/8 | 10.0.0.0–10.255.255.255 |
| 172.16.0.0/12 | 172.16.0.0–172.31.255.255 |
| 192.168.0.0/16 | 192.168.0.0–192.168.255.255 |
These addresses are reserved for private networks and may be reused on disconnected or self-contained networks. The boundaries matter: not every address beginning with 172 or 192 is private-use. For example, 172.15.0.1 and 172.32.0.1 are outside 172.16.0.0/12; 192.167.0.1 and 192.169.0.1 are outside 192.168.0.0/16. IANA’s private-addresses help page explains the ranges, and the IPv4 Special-Purpose Address Space registry records their classifications.
What is the IPv6 equivalent?
IPv6 uses the category name Unique-Local Address (ULA) for the prefix fc00::/7, specified by RFC 4193. IANA lists this prefix as Unique-Local and specifies that it is not globally routed. It is not an IPv4 private range written in a different format. See the IPv6 Special-Purpose Address Space registry.
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How do private-use ranges differ from other special-purpose addresses?
“Special-purpose” is an umbrella registry context, not a synonym for “private.” IANA assigns distinct categories to neighboring blocks, so an address being local, shared, or special-purpose does not by itself make it RFC 1918 private-use.
| Address block | IANA category |
|---|---|
| 100.64.0.0/10 (IPv4) | Shared Address Space |
| 127.0.0.0/8 (IPv4) | Loopback |
| 169.254.0.0/16 (IPv4) | Link Local |
| 192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24 (IPv4) | Documentation |
| fe80::/10 (IPv6) | Link-Local Unicast |
| 2001:db8::/32 and 3fff::/20 (IPv6) | Documentation |
The IPv4 entries are listed in IANA’s IPv4 registry; the IPv6 entries are in IANA’s IPv6 registry. In particular, 100.64.0.0/10 is Shared Address Space under RFC 6598, not part of the RFC 1918 list.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Does a special-purpose address mean it cannot be routed?
No single rule follows from the label alone. IANA records properties such as whether a block is forwardable and globally reachable separately from its category. Those attributes are specific to each allocation, and the registry notes that entries do not guarantee routability in any particular local or global context. Check the relevant entry in the IPv4 registry or IPv6 registry rather than inferring reachability from the words “private” or “special-purpose.”
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