The IMS: IP Multimedia Concepts And Services, Second Edition

Chapter 24. DHCPv6

The Dynamic Host Configuration Protocol for Internet Protocol (IP) Version 6 (DHCPv6), as defined in [RFC3315], is a client–server protocol that allows devices to be configured with management configuration information. DHCP specifically provides clients with dynamically assigned IP addresses using a DHCP server. It also provides other configuration information carried as options: options are extensions to DHCP. "Extending DHCP" means defining a new option.

DHCP messages are exchanged between clients and servers using User Datagram Protocol (UDP) for transport. Clients listen on port 546 for messages, while servers listen on port 547. A client uses a link-local address for transmitting and receiving DHCP messages. A client sends DHCP messages to servers using the link-scoped multicast address "FF02 : : 1 : 2", also known as All_DHCP_Relay_Agents_and_Servers. DHCP relay agents on the client's link allow a DHCP client to send a message to a DHCP server that is not attached to the same link.

A client needs, first, to locate a DHCP server before requesting an IP address and other configuration information. It does so by sending a DHCP solicit message to the multicast address identified earlier. A server willing to answer the request answers with a DHCP advertise message. The client then chooses one of the servers and a DHCP request message. The server responds with a relay message confirming the assigned IP addresses and other configuration information. Because ...