Control

At-A-Glance

DHCP for IPv6
(RFC3315)
L ast updated: March 2008
The Dynamic Host Configuration Protocol for IPv6
(DHCPv6) has been standardized by the IETF through
RFC3315. The Dynamic HostConfiguration Protocol for
IPv6 (DHCP) enables DHCP servers to pass configuration parameters, such as IPv6 network addresses, to IPv6
nodes. It offers the capability of automatic allocation ofreusable network addresses and additional configuration
flexibility. This protocol is a stateful counterpart to "IPv6
Stateless Address Autoconfiguration" (RFC 2462), and
can be used separately, orconcurrently with the latter, to
obtain configuration parameters.
The basic DHCPv6 client-server concept is similar
to using DHCP for IPv4. If a client wishes to receive
configuration parameters, itwill send out a request on
the attached local network to detect available DHCPv6
servers. This done through the “Solicit” and “Advertise”
messages. Well known DHCPv6 Multicast addresses
are used forthis process. Next, the DHCPv6 client will
”Request” parameters from an available server which will
respond with the requested information with a “Reply”
message. The diagram below demonstratesthe sequence of events:
DHCPv6 Client

Reply
Request
Advertise
Solicit

5

DHCPv6 Server

4

The DHCPv6 client will know when it wants to use
DHCPv6, either based upon instruction of anattached
router, or when no default gateway is present. The
default gateway has two configurable bits in an Router
Advertisement (RA) available for this purpose:

•
•

‘O’ bit—When this bit isset, the client can use
DHCPv6 to retrieve Other configuration parameters
(ie: DNS addresses)
‘M’ bit—When this bit is set, the client may use
DHCPv6 to retrieve a Managed IPv6 address from aDHCPv6 server

When a router sends an RA with ‘O’ bit set, but does
not set the ‘M’ bit, the client can do Stateless Address
Autoconfiguration (SLAAC) to obtain its IPv6 address,
and use DHCPv6...