H3C Technologies H3C SecPath F1000-E - Manual (Page 179)

154
3. Otherwise, the DHCP server selects the smallest address pool that contains the IP address of the
receiving interface (if the client and the server reside on the same network segment), or the smallest
address pool that contains the IP address specified in the giaddr field of the client's request (if a
DHCP relay agent is in-between). If no IP address is available in the address pool, the DHCP server
will fail to assign an address to the client because it cannot assign an IP address from the father
address pool to the client. For the configuration of such an address pool, see " Creating a dynamic
address pool for the DHCP server ."
For example, two address pools, 1.1.1.0/24 and 1.1.1.0/25, are configured on the DHCP server. If the IP
address of the interface receiving DHCP requests is 1.1.1.1/25, the DHCP server will select IP addresses
for clients from address pool 1.1.1.0/25. If no IP address is available in the address pool, the DHCP server
will fail to assign addresses to clients. If the IP address of the interface receiving DHCP requests is
1.1.1.130/25, the DHCP server will select IP addresses for clients from the 1.1.1.0/24 address pool.
IP address allocation sequence
A DHCP server assigns an IP address to a client according to the following sequence:
1. The IP address manually bound to the client's MAC address or ID
2. The IP address that was ever assigned to the client
3. The IP address designated by the Option 50 field in the DHCP-DISCOVER message
4. The first assignable IP address found in a proper DHCP address pool
5. The IP address that was a conflict or passed its lease duration
If no IP address is assignable, the server does not respond.
NOTE:
Option 50 is the requested IP address field in DHCP-DISCOVER messages. It is padded by the client to
specify the IP address that the client wants to obtain. The contents to be padded depend on the client.
Configuring the DHCP server in the web interface
DHCP server configuration task list
Complete the following tasks to configure the DHCP server:
Task Remarks
Enabling DHCP
Required.
Enable DHCP globally.
By default, global DHCP is disabled.