User's Manual

30-1
Chapter 30 DHCPv6 Configuration
30.1 Introduction to DHCPv6
DHCPv6 [RFC3315] is the IPv6 version for Dynamic Host Configuration Protocol (DHCP). It is a protocol that
assigns IPv6 address as well as other network configuration parameters such as DNS address, and domain
name to DHCPv6 client, DHCPv6 is a conditional auto address configuration protocol relative to IPv6. In the
conditional address configuration process, DHCPv6 server assigns a complete IPv6 address to client, and
provides DNS address, domain name and other configuration information, maybe the DHCPv6 packet can
transmit through relay delegation, at last the binding of IPv6 address and client can be recorded by DHCPv6
server, all that can enhance the management of network; DHCPv6 server can also provide non state DHCPv6
service, that is only assigns DNS address and domain name and other configuration information but not
assigns IPv6 address, it can solve the bug of IPv6 auto address configuration in non state; DHCPv6 can
provide extend function of DHCPv6 prefix delegation, upstream route can assign address prefix to
downstream route automatically, that achieve the IPv6 address auto assignment in levels of network
environment, and resolved the problem of ISP and IPv6 network dispose.
There are three entities in the DHCPv6 protocol – the client, the relay and the server. The DHCPv6 protocol is
based on the UDP protocol. The DHCPv6 client sends request messages to the DHCP server or DHCP relay
with the destination port as 547, and the DHCPv6 server and relay send replying messages with the
destination port as 546. The DHCPv6 client sends solicit or request messages with the multicast address –
ff02::1:2 for DHCP relay and server.
Figure 30-1 DHCPv6 negotiation
When a DHCPv6 client tries to request an IPv6 address and other configurations from the DHCPv6 server,
the client has to find the location of the DHCP server, and then request configurations from the DHCP server.
1. In the time of located server, the DHCP client tries to find a DHCPv6 server by broadcasting a
SOLICIT packet to all the DHCP delay delegation and server with broadcast address as FF02::1:2.
2. Any DHCP server which receives the request, will reply the client with an ADVERTISE message,
which includes the identity of the server –DUID, and its priority.
3. It is possible that the client receives multiple ADVERTISE messages. The client should select one
and reply it with a REQUEST message to request the address which is advertised in the
ADVERTISE message.
DHCPv6 CLIENT
DHCPv6 SERVER
Solicit (Multicast)
Advertise (Unicast)
Request (Multicast)
Reply (Unicast)