Huawei Quidway S5600 Series Operation Manual page 675

Operation Manual - DHCP
Quidway S5600 Series Ethernet Switches-Release 1510
The dynamic user address entry updating function works as follows: at regular
intervals, the DHCP relay sends a DHCP-REQUEST packet that carries the IP
address assigned to a DHCP client and its own bridge MAC address to the
corresponding DHCP server. If the DHCP server answers with a DHCP-ACK packet,
the IP address is available (it can be assigned again) and the DHCP relay ages out the
corresponding entry in the user address table. If the DHCP server answers with a
DHCP-NAK packet, the IP address is still in use (the lease is not expired) and the
DHCP relay remains the corresponding user address entry unchanged.
Table 3-6 Configure the dynamic user address entry updating function
Enter system view
Enable
handshake
Set the interval at which the
DHCP relay dynamically
updates the user address
entries
IV. Configuring pseudo-DHCP server detection function
If there is an authorized DHCP server in the network, when a client applies for an IP
address, the authorized DHCP server interconnects with the DHCP client. As a result,
the DHCP client obtains an incorrect IP address. Such unauthorized DHCP server is
called a pseudo DHCP server.
After the pseudo DHCP server detection function is enabled on a DHCP relay, when a
DHCP client sends the DHCP-REQUEST message, the DHCP relay can obtain the IP
address of the server that assigns an IP address to the client from the message and
records the assigned IP address as well as the information of the interface receiving
the message. As a result, the administrator can find and deal with the pseudo DHCP
server.
Table 3-7 Configure pseudo-DHCP server detection function
Enter system view
Operation
system-view
DHCP relay dhcp
enable
dhcp-security tracker
{ interval | auto }
Operation
system-view
Huawei Technologies Proprietary
Chapter 3 DHCP Relay Configuration
Command
relay hand
Command
3-8
Description
—
Required
Optional
Description
—