Subnet Ninja Private and Reserved IP Address Ranges
Updated
Reserved Addresses
The Internet Assigned Numbers Authority (IANA) reserves some prefixes for special use. The private ranges used in home and office LANs are one example. Reserved addresses should not appear on the public Internet, and ISPs generally drop packets to or from these "Martian" networks.
| IPv4 | IPv6 | Purpose | Defined in |
|---|---|---|---|
| 0.0.0.0/8 | – | "This network"; 0.0.0.0 means "this host" and is only valid as a source address | RFC 791, RFC 1122 |
| – | ::/128 | Unspecified address | RFC 4291 |
| 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 | fc00::/7 | Private use (IPv6: unique local addresses) | RFC 1918, RFC 4193 |
| 100.64.0.0/10 | – | Shared address space for carrier-grade NAT | RFC 6598 |
| 127.0.0.0/8 | ::1/128 | Loopback (localhost) | RFC 1122, RFC 4291 |
| 169.254.0.0/16 | fe80::/10 | Link-local | RFC 3927, RFC 4291 |
| 192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24 | 2001:db8::/32, 3fff::/20 | Documentation and examples (TEST-NET-1, -2, -3) | RFC 5737, RFC 3849, RFC 9637 |
| 198.18.0.0/15 | – | Network benchmarking | RFC 2544 |
| – | 64:ff9b::/96 | IPv4/IPv6 translation (NAT64) | RFC 6052 |
| 224.0.0.0/4 | ff00::/8 | Multicast | RFC 5771, RFC 4291 |
| 240.0.0.0/4 | – | Reserved for future use | RFC 1112 |
| 255.255.255.255/32 | – | Limited broadcast | RFC 919, RFC 8190 |
Source: IANA IPv4 and IPv6 special-purpose address registries (RFC 6890).
Private Addresses
Private addresses are part of the reserved space and used in most LAN networks. The IPv4 private ranges are defined in RFC 1918 and the IPv6 unique local range in RFC 4193; in practice IPv6 sites use fd00::/8, the locally assigned half of fc00::/7. Networks using private addresses rely on Network Address Translation (NAT) to route traffic to the global internet.
Link Local Address
Link-local addresses are used by devices to auto-configure their own IP address without DHCP. In IPv6, link-local addresses are mandatory and widely used for routing protocol adjacencies.
- 169.254.0.0/16: IPv4 link-local address (APIPA).
- fe80::/10: IPv6 link-local address.
Global Addresses (Public Space)
Global or public IP addresses are unique addresses used by all devices connected to the Internet. IANA allocates them to the five Regional Internet Registries (RIRs): AFRINIC, APNIC, ARIN, LACNIC and RIPE NCC, which assign them to ISPs and organisations.
PA and PI Addresses
- Provider Aggregatable (PA): Addresses allocated by an ISP to an end user. The ISP aggregates these PA addresses and advertises the larger subnet via BGP.
- Provider Independent (PI): Addresses allocated directly by the RIR to the end user. This allows an Autonomous System (AS) to advertise the prefix via BGP to multiple ISPs (Multihoming) and switch providers without changing IPs.