H3C Technologies H3C S10500 Series Switches - Manual (Page 58)

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To do… Use the command… Remarks
Apply an extended address
pool on the interface dhcp server apply ip-pool
pool-name
Optional
By default, the DHCP server has no
extended address pool applied on its
interface, and assigns an IP address
from a common address pool to a
requesting client.
Configuring the DHCP server security functions
Configuration prerequisites
Before performing this configuration, complete the following configurations on the DHCP server:
• Enable DHCP
• Configure the DHCP address pool
Enabling unauthorized DHCP server detection
Unauthorized DHCP servers on a network may assign wrong IP addresses to DHCP clients.
With unauthorized DHCP server detection enabled, the DHCP server checks whether a DHCP request
contains Option 54 (Server Identifier Option). If yes, the DHCP server records the IP address of each
detected DHCP server that assigned an IP address to a requesting DHCP client in the option, and records
the receiving interface. The administrator can use this information to check for unauthorized DHCP
servers.
Follow these steps to enable unauthorized DHCP server detection:
To do… Use the command… Remarks
Enter system view system-view —
Enable unauthorized DHCP server
detection
dhcp server detect
Required
Disabled by default.
NOTE:
With the unauthorized DHCP server detection enabled, the switch logs each detected DHCP server once.
The administrator can use the log information to find unauthorized DHCP servers.
Configuring IP address conflict detection
With IP address conflict detection enabled, before assigning an IP address, the DHCP server pings that
IP address by using ICMP. If the server receives a response within the specified period, it selects and
pings another IP address. If it receives no response, the server continues to ping the IP address until the
specified number of ping packets are sent. If still no response is received, the server assigns the IP
address to the requesting client. (The DHCP client probes the IP address by sending gratuitous ARP
packets.)
Follow these steps to configure IP address conflict detection: