DHCPv6 uses “options” in the variable format section of a DHCPv6message. Several options, necessary for the operation of the protocol, are defined in section 22 of the DHCPv6 specification (RFC 3315). Several other options have been in development and are described in the remainder of this section.
IPv6 Prefix Options for DHCPv6
The “Prefix Option” is used for prefix delegation in DHCPv6. An ISP uses prefix delegation to configure a CPE device (typically a router) with one or more prefixes to use in the customer’s network. This option is specified in RFC 3633 [RFC3633].
DSTM Options for DHCPv6
There are three dual-stack transition mechanism (DSTM) [Bou05], options for DHCPv6. The first two options are used to assign IPv4 addresses to a host using DSTM and to give the address of a DSTM tunnel endpoint. These options are documented in [RB05]
DSTM Ports Option for DHCPv6
The third option DSTM DHCPv6 specifies the ports to be used by a host for IPv4-mapped IPv6 addresses, and is documented in [Shi05]. The progress of all three DSTM options will be synchronized with the progress of the DSTM specification through the IETF.
DNS Configuration options for DHCPv6
There are two DNS configuration options documented in RFC 3646 [RFC3646]. The first passes the IP addresses of a list of DNS servers to a host. The second option passes a list of domains to be used as a domain search list by the host.
NIS/NIS+ Configuration Options for DHCPv6
There are four DHCPv6 options for NIS and NIS+ configuration, which are documented in [RFC3898]. Two of the options provide a list of NIS servers and an NIS domain to a host, and two options provide a list of NIS+ servers and an NIS+ domain.
Time Configuration Options for DHCPv6
There are two DHCPv6 options for time configuration. One option provides a list of NTP servers to the host and is described in RFC 4075 [RFC4075]. The other option provides time zone information to the host and is currently specified by the Internet Draft draft-ietf-dhc-dhcpv6-opt-tz-00 [Kal03].
Client Preferred Prefix option for DHCPv6
The client preferred prefix option allows a client to indicate the prefixes form which it would prefer to have its addresses assigned. This option is documented in [Vij03], and is still under discussion by the DHC WG.
Load Balancing for DHCPv6
DHCPv6 provides for the operation of multiple servers. Under normal circumstances, all servers respond to each request for service and the requesting client picks a server for service. The Internet Draft “Load Balancing for DHCPv6” [Vol02] describes a mechanism through which multiple cooperating DHCPv6 servers can determine which server should respond to a specific client. The DHCPv6 load balancing mechanism was submitted to the IESG for approval as a Proposed Standard in January 2003.