IPv6 addressing in 60 seconds
An IPv6 address is 128 bits, written as eight groups of four hexadecimal digits: 2001:0db8:0000:0000:0000:0000:0000:0001. Two shortening rules make it readable. You can drop leading zeros in each group, and you can replace one run of all-zero groups with ::. The result is 2001:db8::1.
RFC 5952 defines one canonical way to write every address: lowercase, no leading zeros, :: for the longest run of two or more zero groups (the first one on a tie), and never :: for a single zero group. Consistent notation matters when you search logs, compare firewall rules or write documentation. This calculator always outputs the canonical form.
Common prefix sizes
| Prefix | Typical use | Number of /64 networks |
|---|---|---|
| /32 | Allocation to an ISP or large organisation (from an RIR such as APNIC) | 4,294,967,296 |
| /48 | A whole site or enterprise | 65,536 |
| /56 | A home or small-business customer | 256 |
| /64 | A single LAN / VLAN. Required for SLAAC | 1 |
| /127 | Point-to-point router links (RFC 6164) | – |
| /128 | A single host, loopback or anycast address | – |
Plan on nibble boundaries. Prefixes that are multiples of 4 (/48, /52, /56, /60, /64) line up with hex digits, so subnets are easy to read: 2001:db8:abcd:0100::/56, 2001:db8:abcd:0200::/56. Use the split tool above to generate the list.
IPv6 address types
| Prefix | Type |
|---|---|
2000::/3 | Global unicast (public internet) |
fc00::/7 | Unique local addresses (ULA), the IPv6 equivalent of private ranges. In practice fd00::/8 |
fe80::/10 | Link-local. Every interface has one, and it’s used by Neighbor Discovery and routing protocols |
ff00::/8 | Multicast (IPv6 has no broadcast). ff02::1 = all nodes |
::1/128 · ::/128 | Loopback · unspecified |
::ffff:0:0/96 | IPv4-mapped addresses |
2001:db8::/32 | Documentation and examples |
64:ff9b::/96 | NAT64 well-known prefix |