IPv6 Stateless address autoconfiguration is similar to DHCP in IPv4. Routers running IPv6 can give the network prefix and gateway address to clients looking for an IPv6 address. The device needs a global IPv6 address to be able to connect to the network (and internet). IPv6 stateless autoconfiguration is a way for a device to automatically generate global IPv6 addresses without the need for manual configuration or help of a server, such as a Dynamic Host Configuration Protocol (DHCP) server.
- A node can automatically configure its own IPv6 address by appending its 64-bit interface identifier to the 64-bit prefix it receives from a Router Advertisement (RA) message
- The 128-bit IPv6 address is then subjected to duplicate address detection (DAD) to ensure uniqueness
- If the prefixes advertised in the RA messages are globally unique, then the IPv6 addresses configured by the node are also guaranteed to be globally unique.
- Device solicitation messages, which have a value of 133 in the Type field of the ICMP packet header, are sent by hosts at system startup so that the host can immediately autoconfigure without needing to wait for the next scheduled RA message.
- So what happens if there is a duplicate? That’s beyond the CCNA, but normally it will disable the interface for IPv6. There are other cases you can read about in RFC4862 if you like.
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