SLAAC – Stateless Address Auto-Configuration
(SLAAC) is a technique used in IPv6 systems that lets every host on the network to automatically configure a unique IPv6 address without requiring any additional hardware to keep track of which address belongs to which node.
In the context of IPv6 address assignment, the terms “stateless” and “stateful” refer to:
- In a stateful IPv6 address assignment, a server or a node that monitors and tracks of the status of each assignment is required. It tracks the address pool availability and resolves duplicated address conflicts. It also logs every assignment and keeps track of the lease times. An example of a stateful IPv6 assignment is using DHCPv6 (The Dynamic Host Configuration Protocol version 6)
- In a stateless IPv6 address assignment; no server keeps track of what addresses have been assigned and what addresses are still available for an assignment (That is SLAAC). Instead the hosts are responsible to resolve any duplicated address conflicts by following the algorithm: Generate an IPv6 address, run the Duplicate Address Detection (DAD), if the address happens to be in use, generate another one and run DAD again, etc. The challenge with SLAAC is that it does not provide DNS server addresses to hosts and that is why it is not a popular IPv6 implementation the moment.
