IPv6 explained
What is IPv6?
IPv6 (Internet Protocol version 6, RFC 8200) is the successor to IPv4, created to overcome address exhaustion. Each address is 128-bit, written as eight groups of hexadecimal such as 2001:db8::1, giving 2¹²⁸ (≈ 3.4 × 10³⁸) addresses.
The architecture is defined in RFC 4291. The whole space is ::/0; today only the global unicast block 2000::/3 is delegated to RIRs, while the rest is reserved for specific technical roles.
Special-purpose ranges
Key reserved and special blocks (see the IANA IPv6 Special-Purpose registry):
| Range | Purpose | Reference |
|---|---|---|
| ::/128 | Unspecified address tech | RFC 4291 |
| ::1/128 | Loopback tech | RFC 4291 |
| ::ffff:0:0/96 | IPv4-mapped addresses tech | RFC 4291 |
| 64:ff9b::/96 | IPv4/IPv6 translation (NAT64) tech | RFC 6052 |
| 100::/64 | Discard-only block tech | RFC 6666 |
| 2000::/3 | Global unicast — delegated to RIRs RIR | RFC 4291 |
| 2001::/23 | IETF protocol assignments tech | RFC 2928 |
| 2001:db8::/32 | Documentation tech | RFC 3849 |
| 2002::/16 | 6to4 (deprecated) tech | RFC 7526 |
| fc00::/7 | Unique local addresses (ULA) private | RFC 4193 |
| fe80::/10 | Link-local unicast tech | RFC 4291 |
| ff00::/8 | Multicast tech | RFC 4291 |
Allocation to the RIRs
Within global unicast 2000::/3, IANA delegates one /12 to each RIR. These five blocks are the backbone of all current IPv6 assignments (source: IANA IPv6 Global Unicast registry):
| RIR | Block | Service region |
|---|---|---|
| APNIC | 2400::/12 | Asia-Pacific |
| ARIN | 2600::/12 | North America |
| LACNIC | 2800::/12 | Latin America & Caribbean |
| RIPE NCC | 2a00::/12 | Europe, Middle East, Central Asia |
| AFRINIC | 2c00::/12 | Africa |
Smaller historical blocks (e.g. 2001::/16) were assigned earlier; the registry above is authoritative.