Operation Manual - DHCP 
Quidway S3900 Series Ethernet Switches-Release 1510  Chapter 3  DHCP Relay Configuration
 
Huawei Technologies Proprietary 
3-7 
Operation  Command  Description 
Enter interface view 
interface  interface-type 
interface-number 
— 
Enable the address 
checking function 
address-check enable 
Required 
By default, the address 
checking function is disabled 
 
II. Configuring DHCP relay handshake 
When the DHCP client obtains an IP address from the DHCP server through the 
DHCP relay, the DHCP relay records the binding relationship of the IP address and the 
MAC address. After the DHCP relay function is enabled, the DHCP relay sends the 
handshake packet (the DHCP-REQUEST packet) periodically to the DHCP server 
according to the IP address and its MAC address, which are specified in the binding 
relationship.  
z  If the DHCP server returns the DHCP-ACK packet, it indicates that the IP address 
can be assigned. The DHCP relay ages the corresponding entry in the user 
address table.   
z  If the DHCP server returns the DHCP-NAK packet, it indicates that the lease of 
the IP address is not expired. The DHCP relay does not age the corresponding 
entry.  
After the DHCP relay function is disabled, the DHCP relay does not send the 
handshake packet (the DHCP-REQUEST packet) periodically to the DHCP server.   
z  When the DHCP client releases this IP address, the client unicasts the 
DHCP-RELEASE packet to the DHCP server.   
z  The DHCP relay does not process this packet, so the user address entries of the 
DHCP relay cannot be updated in real time.   
Table 3-5 Enable/disable DHCP relay handshake 
Operation  Command  Description 
Enter system view
 
system-view 
— 
Enable DHCP relay 
handshake
 
dhcp relay hand 
enable 
Disable DHCP relay 
handshake
 
dhcp relay hand 
disable 
By default, the DHCP relay 
function is enabled 
Only S3900-EI series 
switches among S3900 
series switches support 
this configuration