DHCP methods adopted by a slave device connected to a host device are disclosed. The method includes: receiving a DHCP discover message from the host device; in response to the DHCP discover message, transmitting a DHCP offer message containing a DHCP renewal time configuration to the host device; receiving a DHCP request message from the host device; and in response to the DHCP request message, transmitting a DHCP acknowledgement message containing a client Internet Protocol (IP) address and the DHCP renewal time configuration to the host device.