H3C Technologies H3C SecPath F1000-E - Manual (Page 233)

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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, refer to
section 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.
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.
Creating a Static Address Pool
for the DHCP Server
Creating a Dynamic Address
Pool for the DHCP Server
Required to configure either of the two
IMPORTANT:
z If the DHCP server and DHCP clients are on the same subnet, make
sure the address pool is on the same network segment as the
interface with the DHCP server enabled; otherwise, the clients will fail
to obtain IP addresses.
z If a DHCP client obtains an IP address via a DHCP relay agent, an IP
address pool on the same network segment as the DHCP relay agent
interface must be configured; otherwise, the client will fail to obtain an
IP address.