3Com WX3000 DHCP Snooping Configuration

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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.

DHCP Snooping Configuration

Follow these steps to configure DHCP snooping:

To do… Use the command… Remarks

Enter system view system-view —

Enable DHCP snooping dhcp-snooping Required

By default, the DHCP snooping

function is disabled.

Enter Ethernet port view interface interface-type

interface-number —