In most cases, the in.ndpd daemon starts up DHCPv6 automatically when it is needed.
For DHCPv4, however, you must reconfigure the DHCP client if DHCPv4 was not configured during as part of the installation process. For complete instructions, see How to Enable a DHCP Client.
With either DHCP protocol, the dhcpagent daemon obtains configuration information that is needed by other processes involved in booting the system. For this reason, the system startup scripts start dhcpagent early in the boot process and wait until the network configuration information from the DHCP server arrives.
At startup, if persistent DHCP configurations exist in the system, the dhcpagent daemon is started as part of the startup script processes. The dhcpagent daemon then configures the network interfaces as described in How DHCP Works.