DHCPv6 Option

DHCPv6 Options and Configuration Parameters RFC3315 and RFC3646

DHCPv6 uses a different option format than DHCPv4. Options in DHCPv6 are encoded using a two-octet option code followed by a two-octet option length, followed by the option data.

Option Format

0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          option-code          |           option-len          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                          option-data                          |
|                      (option-len octets)                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Common DHCPv6 Options

Client Identifier (Option 1)

The Client Identifier option is used to carry a DUID (DHCP Unique Identifier) associated with the client. Each DHCPv6 client and server has a DUID.

The format is:

Code   Len   DUID

+-----+-----+-----+-----+--- | 1 | n | d1 | d2 | ... +-----+-----+-----+-----+---

Server Identifier (Option 2)

The Server Identifier option is used to carry a DUID associated with the server.

The format is:

Code   Len   DUID

+-----+-----+-----+-----+--- | 2 | n | d1 | d2 | ... +-----+-----+-----+-----+---

Identity Association for Non-temporary Addresses (IA_NA) (Option 3)

The IA_NA option is used to carry an IA_NA, the parameters associated with it, and the addresses associated with it.

The format is:

Code   Len   IAID  T1    T2    IA_NA-options

+-----+-----+-----+-----+-----+-----+-----+--- | 3 | n | iaid| t1 | t2 | opt1| opt2| ... +-----+-----+-----+-----+-----+-----+-----+---

Identity Association for Temporary Addresses (IA_TA) (Option 4)

The IA_TA option is used to carry an IA_TA, the parameters associated with it, and the addresses associated with it.

Identity Association Address (IAADDR) (Option 5)

The IAADDR option is used to specify IPv6 addresses associated with an IA_NA or IA_TA.

The format is:

Code   Len   IPv6-address  preferred-lifetime  valid-lifetime  IAADDR-options

+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+--- | 5 | n | a1 | a2 | a3 | a4 | a5 | a6 | a7 | a8 | opt1| ... +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+---

Option Request (Option 6)

The Option Request option is used to identify a list of options in a message between a client and a server.

The format is:

Code   Len   option-code-1  option-code-2  ...

+-----+-----+-----+-----+-----+-----+--- | 6 | n | c1 | c2 | c3 | c4 | ... +-----+-----+-----+-----+-----+-----+---

Preference (Option 7)

The Preference option is sent by servers to control the selection of a server by the client.

The format is:

Code   Len   pref-value

+-----+-----+-----+ | 7 | 1 | pref| +-----+-----+-----+

Elapsed Time (Option 8)

The Elapsed Time option is used to indicate how long a client has been trying to complete a DHCPv6 message exchange.

The format is:

Code   Len   elapsed-time

+-----+-----+-----+-----+ | 8 | 2 | t1 | t2 | +-----+-----+-----+-----+

Relay Message (Option 9)

The Relay Message option is used in a RELAY-FORW or RELAY-REPL message to carry DHCPv6 messages.

DNS Recursive Name Server (Option 23)

The DNS Recursive Name Server option provides a list of one or more IPv6 addresses of DNS recursive name servers.

The format is:

Code   Len   IPv6-address-1  IPv6-address-2  ...

+-----+-----+-----+-----+-----+-----+-----+--- | 23 | n | a1 | a2 | a3 | a4 | a5 | ... +-----+-----+-----+-----+-----+-----+-----+---