Five Key IPv6 Concepts

Here are five keywords that will aid your understanding should you read IPv6 RFC (Request for comments) articles: Stateful and Stateless; Link-Local and Site-Local addresses, also ND (Neighbor Discovery)

1. A stateful IP address is one given by a DHCP server. Usually DHCP gives more information than just the IP address, for example the IP address of the DNS server and also the default gateway.
2. A stateless IP address is one that is automatically configured by router discovery. The host assigns itself an IPv6 address automatically rather like the IPv4 APIPA.
3. Link-Local IPv6 addresses only allow connections with neighbors on that subnet (link), these address beginning with FEC0 are not forwarded by routers. End of story.
4. Site-Local address are routable, but not to the internet, thus hosts with Site-Local IPv6 addresses can use private (not ICANN) IP addresses, AND can connect to any other Site-Local address within the organization. All Site-local address begin with FE80.
5. ND (Neighbor Discovery) Replaces IPv4's ARP and ICMP Router Discovery. The idea is for machines to discover information about their nearest router. In addition, if an IPv6 stack can obtain information about other hosts, then it won't duplicate their IP addresses should it need to use Autoconfiguration.