System administrators need the ability to specify whether stateless autoconfiguration, stateful autoconfiguration, or both should be used.  Router Advertisements include flags specifying which mechanisms a host should use.
 

Small sites consisting of a set of machines attached to a single link should not require the presence of a stateful server as a prior condition for communicating.  Plug-and-play communication is achieved through the use of link-local addresses. 
 

A large site with multiple networks and routers should not require the presence of a stateful address configuration server. In order to generate site-local or global addresses, hosts must determine the prefixes that identify the subnets to which they attach. 
 

Address configuration should facilitate the graceful renumbering of a site's machines. For example, a site may wish to renumber all of its nodes when it switches to a new network service provider.
Renumbering is achieved through the leasing of addresses to interfaces and the assignment of multiple addresses to the same interface. 
 

Manual configuration of individual machines before connecting them to the network should not be required.
Address autoconfiguration assumes that each interface can provide a unique identifier for that interface.  In the simplest case, an interface identifier consists of the interface's link-layer address.