H3C S7500E Series Ethernet Switches Operation Manual

Operation Manual – DHCP
H3C S7500E Series Ethernet Switches Chapter 2 DHCP Server Configuration
2-15
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 device puts a record once
for each DHCP server. The administrator needs to find unauthorized DHCP servers
from the log information.
2.6.3 Configuring IP Address Conflict Detection
To avoid IP address conflicts, the DHCP server checks whether the address to be
assigned is in use via sending ping packets.
The DHCP server pings the IP address to be assigned using ICMP. If the server gets a
response within the specified period, the server will ping another IP address; otherwise,
the server will ping the IP addresses once again until the specified number of ping
packets are sent. If still no response, the server will assign 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:
To do… Use the command… Remarks
Enter system view
system-view
—
Specify the number of
ping packets
dhcp server ping
packets number
Optional
One ping packet by default.
The value 0 indicates that no
ping operation is performed.
Configure a timeout
waiting for ping
responses
dhcp server ping
timeout milliseconds
Optional
500 ms by default.
The value 0 indicates that no
ping operation is performed.
2.7 Configuring the Handling Mode for Option 82
When the DHCP server receives a message with Option 82, if the server is configured
to handle Option 82, it will return a response message carrying Option 82 to assign an
IP address to the requesting client.