19. DHCP ClientMN700004 Rev 01 236The No IP Error ScenarioThe above behavior of the DHCP client assumes that it has successfully received an IPaddress from the DHCP server. If, however, the IP address has not been received, the DHCPclient will keep re-sending the request at predefined time intervals until it eventually managesto negotiate an IP address. (For the exact behavior of the DHCP client and managing itsretransmission timeout, refer to Changing the DHCPDISCOVER Messages RetransmissionTimeout chapter.)NOTES 1. The DHCP client is toggled on/off with the (no) ip address dhcp command.2. You can choose whether to save the downloaded configuration to the non-volatilememory. This is managed with the dhcp-client save-config command.For details on these commands, refer to Configuring the DHCP Client chapter.The entrire startup process is schematically presented in Figure 19-2. It uses asterisks (*), toindicate the following:* This configuration is saved to the non-volatile memory;** File consistency is tested by a check-sum algorithm;**** This means that there is no startup configuration file.The DHCP Negotiation ProcessAs shown in Table 19-1, the parameter negotiation starts with a DHCPDISCOVER broadcastmessage from the client seeking a DHCP server. The DHCP Server responds with aDHCPOFFER unicast message offering configuration parameters (such as an IP address, aMAC address, a domain name, and a lease for the IP address) to the client. The client returnsa DHCPREQUEST broadcast message requesting the offered IP address from the DHCPServer. The DHCP Server responds with a DHCPACK unicast message confirming that the IPaddress has been allocated to the client.Figure 19-1 Obtaining an IP Address from a DHCP Server
