Special IP Addresses (Loopback, Link-Local and More)
Apart from ordinary host addresses, some ranges are reserved for specific purposes.
| Address / Range | Name | Meaning |
|---|---|---|
127.0.0.0/8 (127.0.0.1) |
Loopback | The host itself; localhost |
0.0.0.0 |
Unspecified | "Any" or "unknown"; bind-to-all on servers |
169.254.0.0/16 |
Link-local (APIPA) | Auto-assigned when DHCP fails |
255.255.255.255 |
Limited broadcast | Everyone on the local segment |
224.0.0.0/4 |
Multicast | Group delivery |
192.0.2.0/24 etc. |
Documentation | Examples only (not routable) |
IPv6 Special Addresses
IPv6 has its own reserved ranges (RFC 4291 / RFC 8200). Note there is no broadcast in IPv6 — its role is handled by multicast.
| Address / Range | Name | Meaning |
|---|---|---|
:: |
Unspecified | "No address yet"; source during autoconfig |
::1 |
Loopback | The host itself (like 127.0.0.1) |
fe80::/10 |
Link-local | Auto-configured, valid only on the local link |
fc00::/7 |
Unique Local (ULA) | Private IPv6, like RFC 1918 for IPv4 |
ff00::/8 |
Multicast | Group delivery (replaces broadcast) |
2001:db8::/32 |
Documentation | Examples only (not routable) |
(::/0 you may see in routing tables is the IPv6 default route — a prefix, not an address.)
Looking these up in the IP Lookup tool often returns no registration data, since they are never publicly allocated. See also 127.0.0.1 and localhost.