The client sends a DHCPINFORM message. The client may request specific configuration parameters by including the 'parameter request list' option. The client generates and records a random transaction identifier and inserts that identifier into the 'xid' field. The client places its own network address in the 'ciaddr' field. The client SHOULD NOT request lease time parameters.
The client then unicasts the DHCPINFORM to the DHCP server if it knows the server's address, otherwise it broadcasts the message to the limited (all 1s) broadcast address. DHCPINFORM messages MUST be directed to the 'DHCP server' UDP port.
Once a DHCPACK message with an 'xid' field matching that in the client's DHCPINFORM message arrives from any server, the client is initialized.
If the client does not receive a DHCPACK within a reasonable period of time (60 seconds or 4 tries if using timeout suggested in section 4.1), then it SHOULD display a message informing the user of the problem, and then SHOULD begin network processing using suitable defaults as per Appendix A.