H3C S3600 Series Operation Manual page 595

Operation Manual – DHCP
H3C S3600 Series Ethernet Switches-Release 1510
2.4 DHCP Security Configuration
DHCP security configuration is needed to ensure the security of DHCP service.
2.4.1 Prerequisites
Before configuring DHCP security, you should first complete the DHCP server
configuration (either global address pool-based or interface address pool-based DHCP
server configuration).
2.4.2 Configuring Private DHCP Server Detecting
A private DHCP server on a network also answers IP address request packets and
assigns IP addresses to DHCP clients. However, the IP addresses they assigned may
conflict with those of other hosts. As a result, users cannot normally access networks.
This kind of DHCP servers are known as private DHCP servers.
With the private DHCP server detecting function enabled, when a DHCP client sends
the DHCP-REQUEST packet, the DHCP server tracks the information (such as the IP
address and interface) of the DHCP server which assigns the IP address to the client to
enable the administrator to detect private DHCP servers in time and take proper
measures.
Table 2-20 Enable detection of a private DHCP server
Operation
Enter system view
Enable the private
DHCP
detecting function
2.4.3 Configuring IP Address Detecting
To avoid IP address conflicts caused by assigning the same IP address to multiple
DHCP clients simultaneously, you can configure a DHCP server to detect an IP address
before it assigns the address to a DHCP client.
IP address detecting is achieved by performing ping operations. To detect whether an
IP address is currently in use, the DHCP server sends an ICMP packet with the IP
address to be assigned as the destination and waits for a ping response. If the DHCP
server receives no response within a specified time, it resends an ICMP packet. This
procedure repeats until the DHCP server receives a response or the number of the ping
operations reaches the specified maximum number. The DHCP server assigns the IP
Command
system-view
server
dhcp server detect
2-21
Chapter 2 DHCP Server Configuration
Description
—
Required
By default, the private DHCP
server detecting function is
disabled.