IPv6 Global Unicast Addresses (2000::/3)
Explore IPv6 global unicast addresses in the 2000::/3 range, equivalent to IPv4 public addresses. Learn about the prefix structure, subnetting, and 2001:db8::/32 documentation range.
Detailed Explanation
IPv6 Global Unicast: 2000::/3
Global unicast addresses are the IPv6 equivalent of public IPv4 addresses. They are globally routable and unique across the entire internet.
Range
| Property | Value |
|---|---|
| Range | 2000:: – 3fff:ffff:ffff:ffff:ffff:ffff:ffff:ffff |
| Prefix | 2000::/3 |
| Binary prefix | 001 (first 3 bits) |
Address Structure
| 48 bits | 16 bits | 64 bits |
| Global | Subnet | Interface ID |
| Routing | ID | (host) |
| Prefix | | |
- Global Routing Prefix (48 bits): Assigned by ISP/RIR
- Subnet ID (16 bits): 65,536 subnets per allocation
- Interface ID (64 bits): Host portion
Common Prefixes
| Prefix | Usage |
|---|---|
| 2001:db8::/32 | Documentation and examples (RFC 3849) |
| 2001::/32 | Teredo tunneling |
| 2002::/16 | 6to4 tunneling (deprecated) |
| 2400::/12 | APNIC (Asia-Pacific) |
| 2600::/12 | ARIN (North America) |
| 2a00::/12 | RIPE NCC (Europe) |
The /48 Assignment
A typical organization receives a /48 prefix from their ISP:
2001:0db8:abcd::/48
This gives:
- 65,536 /64 subnets (2^16)
- Each /64 subnet has 18,446,744,073,709,551,616 host addresses (2^64)
Documentation Range: 2001:db8::/32
When writing examples or documentation, always use 2001:db8::/32. This prefix is reserved specifically for documentation and will never be assigned to real networks.
Use Case
A company receives a 2001:db8:cafe::/48 allocation from their ISP and divides it into /64 subnets: 2001:db8:cafe:1::/64 for servers, 2001:db8:cafe:2::/64 for workstations, and 2001:db8:cafe:ffff::/64 for management.