Operation Manual – DHCPH3C S3610&S5510 Series Ethernet Switches Chapter 1 DHCP Overview1-2Note:When residing in a different subnet from the DHCP server, the DHCP client can get theIP address and other configuration parameters from the server via a DHCP relay agent.For information about the DHCP relay agent, refer to Introduction to DHCP RelayAgent.1.2 DHCP Address Allocation1.2.1 Allocation MechanismsDHCP supports three mechanisms for IP address allocation.z Manual allocation: The network administrator assigns an IP address to a client likea WWW server, and DHCP conveys the assigned address to the client.z Automatic allocation: DHCP assigns a permanent IP address to a client.z Dynamic allocation: DHCP assigns an IP address to a client for a limited period oftime, which is called a lease. Most clients obtain their addresses in this way.1.2.2 Dynamic IP Address Allocation ProcessFigure 1-2 Dynamic IP address allocation processAs shown in the figure above, a DHCP client obtains an IP address from a DHCP servervia four steps:1) The client broadcasts a DHCP-DISCOVER message to locate a DHCP server.2) A DHCP server offers configuration parameters such as an IP address to the clientin a DHCP-OFFER message. The sending mode of the DHCP-OFFER isdetermined by the flag field in the DHCP-DISCOVER message. Refer to DHCPMessage Format for related information.
