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what-is-ipv6-stateless-address-auto-configuration.adoc

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sm-hardware/what-is-ipv6-stateless-address-auto-configuration.html
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ipv6, stateless, address, auto configuration
With stateless auto-configuration, hosts do not obtain addresses and other configuration information from a server. Stateless auto-configuration in IPv6 features link-local addresses, multicasting, and the Neighbor Discovery (ND) protocol. IPv6 can generate the interface ID of an address from the underlying data link layer address.

What is IPv6 stateless address auto-configuration?

With stateless auto-configuration, hosts do not obtain addresses and other configuration information from a server. Stateless auto-configuration in IPv6 features link-local addresses, multicasting, and the Neighbor Discovery (ND) protocol. IPv6 can generate the interface ID of an address from the underlying data link layer address.

Stateless auto-configuration and stateful auto-configuration complement each other. For example, the host can use stateless auto-configuration to configure its own addresses, but use stateful auto-configuration to obtain other information. Stateful auto-configuration allows hosts to obtain addresses and other configuration information from a server. Internet Protocol version 6 (IPv6) also defines a method whereby all of the IP addresses on a network can be renumbered at one time. IPv6 defines a method for devices on the network to automatically configure their IP address and other parameters without the need for a server.

Devices perform these steps when using stateless auto-configuration:

  1. Generate a link-local address — The device generates a link-local address, which has 10 bits, followed by 54 zeros, and followed by the 64-bit interface ID.

  2. Test the uniqueness of a link-local address — The node tests to make sure that the link-local address that it generates is not already in use on the local network. The node sends a neighbor solicitation message by using the ND protocol. In response, the local network listens for a neighbor advertisement message, which indicates that another device is already using the link-local address. If so, either a new link-local address must be generated or auto-configuration fails, and another method must be used.

  3. Assign a link-local address — If the device passes the uniqueness test, the device assigns the link-local address to its IP interface. The link-local address can be used for communication on the local network but not over the Internet.

  4. Contact the router — The node tries to contact a local router for more information about continuing the configuration. This contact is performed either by listening for router advertisement messages sent periodically by the routers or by sending a specific router solicitation message to ask a router for information about what to do next.

  5. Provide direction to the node — The router provides direction to the node about how to proceed with auto-configuration. Alternatively, the router tells the host how to determine the global Internet address.

  6. Configure the global address — The host configures itself with its globally unique Internet address. This address is generally formed from a network prefix provided to the host by the router.