he newly formed address, but it is not shown in Figure 3.15. This will result in a /128 IPv6 address configured for a host, which can be used for communications. In the following sections we will look in more depth at some of the details related to IPv6 address management. In Section 3.12.1 we show a detailed example of SLAAC operation based on real-life packet capture, and explain how the address configuration procedures happen in practice. Address States During the SLAAC procedure, IPv6 addresses traverse through different states, which indicate the usability of the address for communications [41]. We will be referring to Router Router Advertisement (with /64 prefix) IID selection Router Solicitation Router Advertisement (with /64 prefix) Creating address by combining /64 prefix + IID Figure 3.15 Overall operation of stateless address autoconfiguration. Introduction to IPv6 these states later within this section when we describe the address autoconfiguration procedure, and in the rest of the book. The state descriptions are the following: Tentative address: The uniqueness of the address on a link is being verified. The address can not yet be used for outbound traffic, and inbound traffic is discarded, except traffic related to DAD (see Section 3.4.7). The tentative address becomes preferred or depre- cated once the DAD has succeeded. Optimistic address: An address that is available for use but that has not yet completed DAD. This state was introduced by RFC 4429 [74] and is not yet supported by all IPv6 stack implementations. The stack should treat optimistic addresses as deprecated, and not to use them if better addresses are available. An optimistic address must not be used to send any packets that may influence neighbors' Neighbor Caches. The address becomes preferred or deprecated once the DAD succeeds. If the DAD fails, the use of the address is ceased immediately - which can possibly cause issues for upper layer protocols that have already started using the optimistic address. For full details of optimist