H3C Technologies H3C SecPath F1000-E - Manual (Page 248)

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Figure 18 DHCP replay agent work process
DHCP-DISCOVER
(broadcast)
DHCP-OFFER
DHCP-REQUEST
(broadcast)
DHCP-ACK
DHCP client DHCP relay DHCP server
DHCP-DISCOVER
(unicast)
DHCP-OFFER
(unicast)
DHCP-REQUEST
(unicast)
DHCP-ACK
(unicast)
As shown in
Figure 18 , the DHCP relay agent works as follows:
1. After receiving a DHCP-DISCOVER or DHCP-REQUEST broadcast message from a DHCP client,
the DHCP relay agent fills the giaddr field of the message with its IP address and forwards the
message to the designated DHCP server in unicast mode.
2. Based on the giaddr field, the DHCP server returns an IP address and other configuration
parameters to the relay agent, which conveys them to the client.
DHCP Relay Agent Configuration Task List
Complete the following tasks to configure the DHCP relay agent:
Task Remarks
Enabling DHCP and
Configuring Advanced
Parameters for the DHCP Relay
Agent
Required
Enable DHCP globally and configure advanced DHCP parameters.
By default, global DHCP is disabled.
Creating a DHCP Server Group
Required
To improve reliability, you can specify several DHCP servers as a group on
the DHCP relay agent and correlate a relay agent interface with the server
group. When the interface receives requesting messages from clients, the
relay agent will forward them to all the DHCP servers of the group.