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IPv6 reorganized addressing completely. No broadcast, several new address types, and multicast that actually works at scale. The good news: the prefixes are standardized, so you can identify address types by inspection.
| Prefix | Type | Purpose |
|---|---|---|
| 2000::/3 | Global Unicast (GUA) | Public internet-routable addresses |
| fe80::/10 | Link-Local | Same-link communication, always present |
| fc00::/7 | Unique Local (ULA) | Private, similar to RFC 1918 |
| ff00::/8 | Multicast | Group communication (replaces broadcast) |
| ::1/128 | Loopback | Local host |
| ::/128 | Unspecified | Source before address assignment |
| 2001:db8::/32 | Documentation | For docs and examples only |
`2000::/3` covers `2000::` through `3fff:ffff:...`. That's why almost every real-world IPv6 address starts with a `2` or `3`. Link-local addresses start with `fe80`. Unique Local starts with `fc` or `fd`.
IPv4 broadcast flooded every host in a subnet, waking up CPUs that had no business processing the traffic. IPv6 replaces broadcast with multicast: only hosts that have explicitly joined a group receive the traffic. This dramatically reduces noise on large segments.
Unicast is one-to-one. Multicast is one-to-many. Anycast is one-to-nearest — the same address is configured on multiple devices, and the network routes to whichever is closest. Anycast is used heavily in DNS (root servers, public resolvers like 1.1.1.1 use it) and increasingly in IPv6 deployments.
From a host's perspective, anycast is invisible — it just sends to the address and gets a response. The routing magic happens in the network. IPv6 anycast is defined for the subnet-router anycast address (all-zero interface ID on a router's subnet), but application-level anycast is more common in practice.
You're reviewing a capture and see four IPv6 destinations: fd12:3456::1, 2001:db8:1::5, fe80::1, and ff02::1. What type is each?
Select the safest next action.
Once you internalize the prefix table, address type identification is instant. Practice on random captures until the prefixes are reflex.
Next lesson digs into the three unicast types you'll actually configure: GUA, link-local, and ULA.
Finish the lesson once you have worked through the material. This awards ★ 35 XP.