3com WX3000 Manuel D’Utilisation

 

2-6 

Enter system view 

— 

Create a static 
IP-to-MAC binding  

dhcp-security static ip-address 
mac-address 

Optional 

Not created by default. 

Enter interface view 

interface interface-type interface-number 

— 

Enable the address 
checking function 

Required 

Disabled by default. 

 

z 

The  address-check enable command is independent of other commands of the DHCP relay 

agent. That is, the invalid address check takes effect when this command is executed, regardless 

of whether other commands (such as the command to enable DHCP) are used. 

z 

Before executing the address-check enable command on the interface connected to the DHCP 

server, you need to configure the static binding of the IP address to the MAC address of the DHCP 

server. Otherwise, the DHCP client will fail to obtain an IP address. 

 

After relaying an IP address from the DHCP server to the DHCP client, the DHCP relay agent can 

automatically record the client’s IP-to-MAC binding and generate a dynamic address entry. But as a 

DHCP relay agent does not process DHCP-RELEASE packets, which are sent to DHCP servers by 

DHCP clients through unicast when the DHCP clients release IP addresses, the user address entries 

maintained by the DHCP cannot be updated in time. You can solve this problem by enabling the DHCP 

relay agent handshake function and configuring the dynamic client address entry updating interval. 

After the handshake function is enabled, the DHCP relay agent sends the handshake packet (the 

DHCP-REQUEST packet) periodically to the DHCP server using a client’s IP address and its own MAC 

address.  

z 

If the DHCP relay agent receives the DHCP-ACK packet from the DHCP server, or receives no 

response from the server within a specified period, the IP address can be assigned. The DHCP 

relay agent ages out the corresponding entry in the client address table.  

z 

If the DHCP relay agent receives the DHCP-NAK packet from the DHCP server, the lease of the IP 

address does not expire. The DHCP relay agent does not age out the corresponding entry. 

Follow these steps to configure the dynamic user address entry updating function: 

Enter system view 

— 

Enable the DHCP relay agent 
handshake function 

Optional 

Enabled by default.