Dhcp Address Allocation; Allocation Mechanisms; Dynamic Ip Address Allocation Process - 3Com 4500G Family Configuration Manual

A DHCP client can get an IP address and other configuration parameters from a DHCP server on
another subnet via a DHCP relay agent. For information about the DHCP relay agent, refer to
Introduction to DHCP Relay

DHCP Address Allocation

Allocation Mechanisms

DHCP supports three mechanisms for IP address allocation.
Manual allocation: The network administrator assigns an IP address to a client like a WWW server,
and DHCP conveys the assigned address to the client.
Automatic allocation: DHCP assigns a permanent IP address to a client.
Dynamic allocation: DHCP assigns an IP address to a client for a limited period of time, which is
called a lease. Most DHCP clients obtain their addresses in this way.

Dynamic IP Address Allocation Process

Figure 1-2 Dynamic IP address allocation process
As shown in Figure
1) The client broadcasts a DHCP-DISCOVER message to locate a DHCP server.
2) A DHCP server offers configuration parameters including an IP address to the client in a
DHCP-OFFER message. The sending mode of the DHCP-OFFER message is determined by the
flag field in the DHCP-DISCOVER message. Refer to
information.
3) If several DHCP servers send offers to the client, the client accepts the first received offer, and
broadcasts it in a DHCP-REQUEST message to formally request the IP address.
4) All DHCP servers receive the DHCP-REQUEST message, but only the server from which the client
accepts the offered IP address responds. The server returns a DHCP-ACK message to the client,
confirming that the IP address has been allocated to the client, or a DHCP-NAK unicast message,
denying the IP address allocation.
Agent.
1-2, a DHCP client obtains an IP address from a DHCP server via four steps:
DHCP Message Format
1-2
for related