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2.8.4. IPv6 Addressing
Why IPv6: IPv4 has approximately 4.3 billion addresses. IPv6 has 340 undecillion (3.4 × 10^38). Address exhaustion—and the complexity of NAT—drove IPv6 adoption.
IPv6 Format:
- 128 bits, written as eight groups of four hexadecimal digits
- Full:
2001:0db8:85a3:0000:0000:8a2e:0370:7334 - Compressed (omit leading zeros,
::for consecutive zero groups):2001:db8:85a3::8a2e:370:7334
IPv6 Address Types:
| Type | Prefix | Scope / Use |
|---|---|---|
| Global unicast | 2000::/3 | Publicly routable on the internet |
| Unique local | fc00::/7 (fd00::/8 in practice) | Private addressing, like RFC 1918 in IPv4; not routed on the internet |
| Link-local | fe80::/10 | Local link only; every IPv6 interface configures one automatically; never routed |
| Multicast | ff00::/8 | One-to-group delivery (IPv6 has no broadcast) |
| Loopback | ::1 | This device (like 127.0.0.1) |
IPv6/IPv4 Coexistence:
- Dual stack: Run both IPv4 and IPv6 simultaneously (most common transition approach)
- Tunneling: Encapsulate IPv6 packets inside IPv4 for transport across IPv4-only networks
- NAT64: Translate between IPv6-only and IPv4-only hosts
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Written byAlvin Varughese
Founder•20 professional certifications