H3C Technologies H3C S7500E Series Switches - Manual (Page 72)

6-7
To do… Use the command… Remarks
Configure the refresh interval
dhcp relay security tracker
{ interval | auto }
Optional
auto by default. (auto interval is calculated
by the relay agent according to the number
of client entries.)
Enabling unauthorized DHCP servers detection
There are unauthorized DHCP servers on networks, which reply DHCP clients with wrong IP
addresses.
With this feature enabled, upon receiving a DHCP request, the DHCP relay agent will record the IP
address of the DHCP server which assigned an IP address to the DHCP client and the receiving
interface. The administrator can use this information to check out any DHCP unauthorized 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 relay server-detect
Required
Disabled by default.
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. After the
information of recorded DHCP servers is cleared, the relay agent will re-record server information
following this mechanism.
Configuring the DHCP Relay Agent to Send a DHCP-Release Request
This task allows you to release a client’s IP address manually on the DHCP relay agent. After you
configure this task, the DHCP relay agent actively sends a DHCP-RELEASE request that contains the
client’s IP address to be released. Upon receiving the DHCP-RELEASE request, the DHCP server
then releases the IP address for the client; meanwhile, the client’s IP-to-MAC binding entry is removed
from the DHCP relay agent.
Follow these steps to configure the DHCP relay agent in system view to send a DHCP-RELEASE
request:
To do… Use the command… Remarks
Enter system view system-view —