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Stateless DHCPv6
Stateless DHCPv6 enables a device that has obtained an IPv6 address/prefix to get other
configuration parameters from a DHCPv6 server.
The device performs stateless DHCPv6 if an RA message with the following flags is received from
the router during stateless address autoconfiguration:
• The managed address configuration flag (M flag) is set to 0.
• The other stateful configuration flag (O flag) is set to 1.
Figure 66 Stateless DHCPv6 operation
As shown in Figure 66, stateless DHCPv6 operates in the following steps:
1. The DHCPv6 client sends an Information-request message to the multicast address of all
DHCPv6 servers and DHCPv6 relay agents. The Information-request message contains an
Option Request option that specifies the requested configuration parameters.
2. The DHCPv6 server returns to the client a Reply message containing the requested
configuration parameters.
3. The client checks the Reply message. If the obtained configuration parameters match those
requested in the Information-request message, the client uses these parameters to complete
configuration. If not, the client ignores the configuration parameters. If the client receives
multiple replies with configuration parameters matching those requested in the
Information-request message, it uses the first received reply.
DHCPv6 options
Option 18
Option 18, also called the interface-ID option, is used by the DHCPv6 relay agent to determine the
interface to use to forward RELAY-REPLY message.
The DHCPv6 snooping device adds Option 18 to the received DHCPv6 request message before
forwarding it to the DHCPv6 server. The server then assigns IP address to the client based on the
client information in Option 18.
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