HP-UX IP Address and Client Management Administrator's Guide HP-UX 11i v2, HP-UX 11i v3

• 546
DHCP servers use this client port as the destination port to send messages to clients and
relays. In addition, the relays or agents use this port as the destination port for messages
sent to the clients.
• 547
DHCP clients use this agent port as the destination port to send messages to agents or relays.
In addition, relays use this port as the destination port for messages sent to the servers.
For more information on port reference, refer to the following link:
http://www.iana.org/assignments/port-numbers
Multicast Addresses
DHCPv6 uses the following multicast addresses:
• All DHCP Agents address - FF02::1:2
DHCP clients use this link-scoped multicast address to communicate with the on-link agent.
All agents within the same DHCP domain belong to this multicast group.
• All DHCP Servers address - FF05::1:3
DHCP clients or relays use this site-scoped multicast address to communicate with servers
in one of the following scenarios:
— When they need to send messages to all servers.
— When they do not know the server’s unicast address.
All servers within the site belong to this multicast group.
See HP-UX IPv6 Porting Guide, available at
http://www.docs.hp.com/en/netcom.html#IPv6, for more information about
link-local and site-local addresses.
How DHCPv6 Works
This section describes how the DHCPv6 software works.
It discusses the following topics:
• “Client/Server Operation” (page 48)
• “Identifying and Managing IPv6 Addresses” (page 50)
Client/Server Operation
This section describes how the DHCPv6 server and the client communicate with each other.
Servers and clients on the same link communicate directly with each other.
The DHCPv6 client initiates the message interaction by sending a SOLICIT message. It uses the
SOLICIT message to locate DHCPv6 servers, which are able to provide an IPv6 address and
other configuration parameters. Multiple servers respond to the client’s message with a DHCP
ADVERTISE message. The DHCP ADVERTISE message contains a preference value, which
indicates the server’s ability to offer services to the client. You need to set this preference value
for a server. See “The dhcpv6d Server Daemon” (page 127) for more information.
The server preference variable is an unsigned single octet value, with the lowest preference value
being 0 and the highest 255. Clients choose higher preference servers over lower preference
servers to configure their interfaces.
The client then sends the DHCP REQUEST message to the server, which is able to provide the
required configuration parameters.
Figure 1-4 depicts how the client and the server, on the same link, communicate with each other.
48 Overview