IPv6 (Internet Protocol version 6)
IPv6 was developed to address IPv4’s address exhaustion problem - providing 340 undecillion addresses to ensure we’ll never run out again.
Address Structure and Format
- 128-bit addresses written in hexadecimal notation (compared to IPv4’s 32-bit decimal)
- Format:
2001:0db8:85a3:0000:0000:8a2e:0370:7334 - Eight groups of four hexadecimal digits separated by colons
- Leading zeros can be omitted:
2001:db8:85a3:0:0:8a2e:370:7334 - Consecutive groups of zeros can be compressed with
::(only once per address):2001:db8:85a3::8a2e:370:7334
Address Types
| Address Type | Purpose | Example | Scope |
|---|---|---|---|
| Global Unicast | Internet routable | 2001:db8::/32 |
Global |
| Link-Local | Auto-configured on each interface | fe80::/10 |
Local link only |
| Unique Local | Private addressing | fc00::/7 or fd00::/8 |
Organization |
| Multicast | One-to-many communication | ff00::/8 |
Variable |
| Anycast | Nearest instance of service | Same as unicast | Variable |
Key Differences from IPv4
- No broadcast - replaced with multicast
- No NAT required - enough addresses for end-to-end connectivity
- Built-in IPSec support - security is mandatory
- Simplified header - only 8 fields vs IPv4’s 14
- Stateless Address Auto-Configuration (SLAAC) - devices can configure themselves
Notes
- IPv6 addresses are slowly replacing IPv4 globally
- Dual-stack networks support both IPv4 and IPv6 during transition
- IPv6 has superior routing efficiency and simplified header processing