IPv6 Tutorial
The pool of available IPv4 addresses has been shrinking for years. NAT has bought time by letting many private hosts share one public address, but it comes with its own headaches — overlapping private ranges, broken end-to-end connectivity, extra complexity for some applications. On top of that, it’s no longer just PCs and laptops asking for an address; phones, sensors, appliances and all kinds of other devices now need one too. IPv6 was designed as the long-term fix for all of this.
IPv6 was published by the IETF in 1998 as IPv4’s eventual replacement. (If you’re wondering what happened to “IPv5” — it was an experimental protocol that was never actually deployed, so the next real version jumped straight to 6.)
The headline difference is address size: IPv4 uses 32 bits, giving roughly 4.29 billion possible addresses (and in practice a fair chunk of those are set aside for special use, so only about 3.7 billion are actually assignable). IPv6 uses 128 bits — 2128, or about 3.4 × 1038 addresses. There’s really no practical way to describe how much larger that is; it’s safe to say we won’t be running out again.
IPv6 address types
| Type | Description |
|---|---|
| Unicast | One-to-one. Covers global, link-local and (now-deprecated) site-local addresses. Identifies a single interface. |
| Multicast | One-to-many. Delivered to every interface that’s a member of the group identified by the address — this is what replaces IPv4’s broadcast. |
| Anycast | One-to-nearest. Allocated out of the unicast range, but delivered to whichever member interface is closest according to the routing protocol in use. |
A single interface isn’t limited to one address — it can hold several addresses of any of these types at once.
Note: IPv6 has no broadcast address at all.
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