Principles of Stateless Address Autoconfiguration

Stateless address allocation is implemented using ND. ND replaces the Address Resolution Protocol (ARP) and ICMP Router Discovery on an IPv4 network. ND also provides functions such as neighbor unreachability detection (NUD), duplicate address detection (DAD), and address autoconfiguration.

The process of stateless address autoconfiguration is as follows:

  1. After a client is started, a link-local address is generated for the client by prepending the link-local prefix FE80::0 to the interface ID.

  2. The client performs Duplicate Address Detection (DAD) on the link-local address by sending a Neighbor Solicitation (NS) message in the broadcast domain. If the client receives a Neighbor Advertisement (NA) message from another device, it indicates the link-local address is a duplicate address. Therefore, another link-local address needs to be generated for the client. After another link-local address is generated, the client still needs to perform DAD on the link-local address until a unique link-local address is obtained.

  3. The client sends a Router Solicitation (RS) message.

  4. The router replies with a Router Advertisement (RA) message, containing the following information:

    • Whether address autoconfiguration is adopted

    • Supported address autoconfiguration modes (stateless or stateful)

    • One or multiple link prefixes (Nodes on the local link can perform address autoconfiguration by using these address prefixes)

    • Lifetime of link prefixes

    • Whether the router sending an RA message can be used as the default router

      If the router can be used as the default router, the lifetime, expressed in seconds, of the default router is also contained in the message.

    • Other configuration information about the client, such as the hop limit and the MTU of the packet initiated by the client

  5. The client receives an RA message from the router. If stateless address autoconfiguration is specified in the RA message, and the RA message contains correct link prefixes, the link prefixes together with interface IDs are used to generate global unicast addresses. Then, DAD is performed on each address. If the RA message carries a flag, indicating that other configuration information in addition to the IP address needs to be obtained in the stateful manner, the client needs to send a DHCPv6 Information-Request message containing the required configuration information. If stateful address autoconfiguration is specified in the RA message, the client sends a DHCPv6 Solicit message to obtain an address and other configuration information.

Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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