Ruijie RG-S2900G-E Series, Configuration Manual

Page: 375 / 943

Configuration Guide DHCPv6 Configuration
Request message to solicit for configuration information, and the DHCP server will send Reply
message after completing the allocation of parameters.
As mentioned above, such a 4-message interaction is very similar to the 4-message interaction
in DHCPv4 (Discover - Offer - Request - Reply). Certainly, DHCPv6 has made further
modifications and expansions.

Multicast is used instead of broadcast because broadcast has been abolished in
the IPv6 network.

By utilizing the option of Rapid Commit, the 4-message interaction can be
simplified into 2-message interaction (Solicit - Reply).

New DHCP message structure, DHCPv6 has made huge modifications to the
original DHCPv4 message, and has removed optional parameters in the header
of DHCP message. Only few fields to be used in all interactions are preserved.
Other optional fields are all encapsulated in the option field of the DHCP
message. During the interaction with the DHCP server and the DHCP relay, the
DHCP message sent by the DHCP client to the DHCP server will be wholly
encapsulated in the DHCP relay message as an option.

New address parameters. As mentioned above, in DHCPv6, the address field is
deleted from the fixed header of the DHCP message, and the entire address
parameters and relevant time parameters are encapsulated in an option called
IA (Identity Association). Each DHCPv6 client is associated with one IA, and
each IA can contain multiple addresses and relevant time information. The
corresponding IA can be generated in accordance with the type of address,
such as IA_NA (Identity association for non-temporary addresses) and IA_TA
(Identity association for temporary addresses).

New DHCP client/server identifier, namely DUID (DHCP Unique Identifier).

Stateless DHCPv6 auto-configuration. During the auto-configuration of network
nodes, the address configuration is independent from parameter configuration,
and each corresponding configuration can be acquired via the DHCP protocol,
which means network nodes can acquire other non-address parameters from
the DHCPv6 server. Compared with the allocation method used in DHCPv4, this
is a critical change. Relevant information is detailed in RFC3736.

Prefix delegation. Apart from IPv6 address, network prefix can also be
delegated via DHCPv6. This also accredits to the definition of IA in DHCPv6. A
prefix can be delegated to the client in the form of address (or time parameter,
etc) only by expanding the type of IA. Such a new type of IA is called IA_PD
(Identity Association for Prefix Delegation), and it is detailed in RFC3633.
Introduction to the DHCPv6 Server
The DHCPv6 server realizes the allocation of IAPD and IANA. The allocation of IANA refers to
the automatic allocation of IPv6 address to the DHCP client, which is similar to DHCPv4. The
allocation of IAPD allows flexible site-level auto-configuration to control the address range of