3com WX3000 Manuel D’Utilisation

 

3-5 

z 

The resources on the server are exhausted, so the server does not respond to other requests.  

z 

After receiving such type of packets, a device needs to send them to the CPU for processing. Too 

many request packets cause high CPU usage rate. As a result, the CPU cannot work normally.  

The device can filter invalid IP packets through the DHCP-snooping table and IP static binding table.  

After DHCP snooping is enabled on a device, a DHCP-snooping table is generated. It is used to record 

IP addresses obtained from the DHCP server, MAC addresses, the number of the port through which a 

client is connected to the DHCP-snooping-enabled device, and the number of the VLAN to which the 

port belongs to. These records are saved as entries in the DHCP-snooping table.  

The DHCP-snooping table only records information about clients that obtains IP address dynamically 

through DHCP. If a fixed IP address is configured for a client, the IP address and MAC address of the 

client cannot be recorded in the DHCP-snooping table. Consequently, this client cannot pass the IP 

filtering of the DHCP-snooping table, thus it cannot access external networks. 

To solve this problem, the device supports the configuration of static binding table entries, that is, the 

binding relationship between IP address, MAC address, and the port connecting to the client, so that 

packets of the client can be correctly forwarded.  

The device can filter IP packets in the following two modes:  

z 

Filtering the source IP address in a packet. If the source IP address and the number of the port that 

receives the packet are consistent with entries in the DHCP-snooping table or static binding table, 

the device regards the packet as a valid packet and forwards it; otherwise, the device drops it 

directly.  

z 

Filtering the source IP address and the source MAC address in a packet. If the source IP address 

and source MAC address in the packet, and the number of the port that receives the packet are 

consistent with entries in the DHCP-snooping table or static binding table, the device regards the 

packet as a valid packet and forwards it; otherwise, the device drops it directly.  

Follow these steps to configure DHCP snooping: 

Enter system view 

— 

Enable DHCP snooping  

Required 

By default, the DHCP snooping 
function is disabled. 

Enter Ethernet port view 

interface interface-type 
interface-number 

—