View source for DHCPv6

{{Short description|Protocol for statefully assigning IPv6 addresses on an IPv6 network}}
{{IPstack}}
The '''Dynamic Host Configuration Protocol version 6''' ('''DHCPv6''') is a [[network protocol]] for configuring [[IPv6|Internet Protocol version 6]] (IPv6) [[host (network)|hosts]] with [[IP address]]es, [[Classless Inter-Domain Routing|IP prefixes]], [[default route]], local segment [[Maximum transmission unit|MTU]], and other configuration data required to operate in an IPv6 network. It is not just the IPv6 equivalent of the [[Dynamic Host Configuration Protocol]] for [[IPv4]].

IPv6 hosts may automatically generate IP addresses internally using [[IPv6#Stateless address autoconfiguration (SLAAC)|stateless address autoconfiguration]] (SLAAC), or they may be assigned configuration data with DHCPv6, or both.

IPv6 hosts that use stateless autoconfiguration may need information other than what SLAAC provides on a given network. DHCPv6 can provide this information whether it is being used to assign IP addresses or not. DHCPv6 can provide host with the addresses of [[Domain Name System]] (DNS) servers, but they can also be provided through [[Neighbor Discovery Protocol]], which is the mechanism for stateless autoconfiguration.{{Ref RFC|4339}}

Many IPv6 routers, such as routers for residential networks, must be configured automatically with no operator intervention. Such routers require not only an IPv6 address for use in communicating with upstream routers, but also an IPv6 prefix for use in configuring devices on the downstream side of the router. DHCPv6 [[prefix delegation]] provides a mechanism for configuring such routers.

==Operation==

===Port numbers===
Clients listen for DHCP messages on [[User Datagram Protocol|UDP]] port 546. Servers and relay agents listen for DHCP messages on UDP port 547.{{Ref RFC|8415|rsection=7.2}}

===Identifiers===
====DHCP unique identifier====
The DHCP unique identifier (DUID) is used by a client to get an IP address from a DHCPv6 server. It has a 2-byte DUID type field, and a variable-length identifier field up to 128 bytes. Its actual length depends on its type. The server compares the DUID with its database and delivers configuration data (address, lease times, DNS servers, etc.) to the client.

Four DUID types are identified:{{Ref RFC|8415|rsection=11}}

* Link-layer address plus time (DUID-LLT)
* Vendor-assigned unique ID based on enterprise number (DUID-EN)
* Link-layer address (DUID-LL)
* UUID-based DUID (DUID-UUID)

====RFC 6939: Client Link-Layer Address Option====
Due to the fact that it is difficult to manage multiple identifiers in a dual-stack environment, and the fact that DUIDs are simply not optimal for some situations, [[rfc:6939|RFC 6939]] was released, giving a way to identify a host based on its [[MAC address]].  It defines a way for a DHCPv6 relay to pass that information to a DHCPv6 server.

===Example===
In this example, without rapid-commit present, the server's link-local address is {{IPaddr|fe80::0011:22ff:fe33:5566}} and the client's link-local address is {{IPaddr|fe80::aabb:ccff:fedd:eeff}}.
* Client sends a ''solicit'' from [{{IPaddr|fe80::aabb:ccff:fedd:eeff}}]:546 to multicast address [{{IPaddr|ff02::1:2}}]:547.{{Ref RFC|8415|rsection=14}}
* Server replies with an ''advertise'' from [{{IPaddr|fe80::0011:22ff:fe33:5566}}]:547 to [{{IPaddr|fe80::aabb:ccff:fedd:eeff}}]:546.
* Client replies with a ''request'' from [{{IPaddr|fe80::aabb:ccff:fedd:eeff}}]:546 to [{{IPaddr|ff02::1:2}}]:547.
* Server finishes with a ''reply'' from [{{IPaddr|fe80::0011:22ff:fe33:5566}}]:547 to [{{IPaddr|fe80::aabb:ccff:fedd:eeff}}]:546.

=== DHCPv6 Message types ===
This table lists the DHCPv6 message types.
{| class="wikitable sortable"
|+DHCPv6 Message Types
!Code
!Name
!RFC
|-
|1
|SOLICIT
|RFC 8415
|-
|2
|ADVERTISE
|RFC 8415
|-
|3
|REQUEST
|RFC 8415
|-
|4
|CONFIRM
|RFC 8415
|-
|5
|RENEW
|RFC 8415
|-
|6
|REBIND
|RFC 8415
|-
|7
|REPLY
|RFC 8415
|-
|8
|RELEASE
|RFC 8415
|-
|9
|DECLINE
|RFC 8415
|-
|10
|RECONFIGURE
|RFC 8415
|-
|11
|INFORMATION-REQUEST
|RFC 8415
|-
|12
|RELAY-FORW
|RFC 8415
|-
|13
|RELAY-REPL
|RFC 8415
|-
|14
|LEASEQUERY
|RFC 5007
|-
|15
|LEASEQUERY-REPLY
|RFC 5007
|-
|16
|LEASEQUERY-DONE
|RFC 5460
|-
|17
|LEASEQUERY-DATA
|RFC 5460
|-
|18
|RECONFIGURE-REQUEST
|RFC 6977
|-
|19
|RECONFIGURE-REPLY
|RFC 6977
|-
|20
|DHCPV4-QUERY
|RFC 7341
|-
|21
|DHCPV4-RESPONSE
|RFC 7341
|-
|22
|ACTIVELEASEQUERY
|RFC 7653
|-
|23
|STARTTLS
|RFC 7653
|}
==IETF standards==
* {{IETF RFC|8415|link=no}}, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)" - Obsoletes RFC 3315, RFC 3633, RFC 3736, RFC 4242, RFC 7083, RFC 7283, RFC 7550.
* {{IETF RFC|3319|link=no}}, "Dynamic Host Configuration Protocol (DHCPv6) Options for Session Initiation Protocol (SIP) Servers"
* {{IETF RFC|3646|link=no}}, "DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)"
* {{IETF RFC|4704|link=no}}, "The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN) Option"
* {{IETF RFC|5007|link=no}}, "DHCPv6 Leasequery" support
* {{IETF RFC|6221|link=no}}, "Lightweight DHCPv6 Relay Agent" (LDRA) - Updates RFC 3315, Errata
* {{IETF RFC|6355|link=no}}, "Definition of the UUID-Based DHCPv6 Unique Identifier (DUID-UUID)"
* {{IETF RFC|6939|link=no}}, "Client Link-Layer Address Option in DHCPv6"
* {{IETF RFC|7653|link=no}}, "DHCPv6 Active Leasequery"

== See also ==
* [[Comparison of DHCP server software]]
* [[Dynamic Host Configuration Protocol]] (DHCP)
* [[Neighbor Discovery Protocol]], which also supports [https://www.rfc-editor.org/rfc/rfc8106.html#section-5.1 DNS Configuration]
* [[Prefix delegation]], which allows a DHCPv6 client to obtain a whole prefix.

==References==
{{Reflist}}

==External links==
{{Wikiversity | DHCPv6}}
* [https://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xhtml IANA DHCPv6 Parameters]
* [http://ipv6int.net/software/index.html#dhcpv6 IPv6 Intelligence: DHCPv6], comparison of DHCPv6 packages and implementations (Last updated: April, 2009)
* [https://www.ipv6ready.org/db/index.php/public/search/?l=&c=&ds=&de=&pc=&ap=2&oem=&etc=D&fw=&vn=&do=1&o=6 IPv6 Ready: DHCPv6], list of IPv6 Phase II Certified DHCPv6 implementations (Last updated: December, 2012)

{{IPv6}}

[[Category:IPv6]]
[[Category:Application layer protocols]]

[[de:Dynamic Host Configuration Protocol#DHCPv6]]