3com WX3000 Manuel D’Utilisation

 

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After you enable the ARP attack detection function, the device will check the following items of an ARP 

packet: the source MAC address, source IP address, port number of the port receiving the ARP packet, 

and the ID of the VLAN the port resides. If these items match the entries of the DHCP snooping table or 

the manual configured IP binding table, the device will forward the ARP packet; if not, the device 

discards the ARP packet.  

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With trusted ports configured, ARP packets coming from the trusted ports will not be checked, 

while those from other ports will be checked through the DHCP snooping table or the manually 

configured IP binding table.  

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With the ARP restricted forwarding function enabled, ARP request packets are forwarded through 

trusted ports only; ARP response packets are forwarded according to the MAC addresses in the 

packets, or through trusted ports if the MAC address table contains no such destination MAC 

addresses. 

The following are the characteristics of gratuitous ARP packets: 

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Both source and destination IP addresses carried in a gratuitous ARP packet are the local 

addresses, and the source MAC address carried in it is the local MAC addresses. 

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If a device finds that the IP addresses carried in a received gratuitous packet conflict with those of 

its own, it returns an ARP response to the sending device to notify of the IP address conflict. 

By sending gratuitous ARP packets, a network device can: 

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Determine whether or not IP address conflicts exist between it and other network devices. 

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Trigger other network devices to update its hardware address stored in their caches. 

The gratuitous ARP packet learning function: 

When the gratuitous ARP packet learning function is enabled on a device and the device receives a 

gratuitous ARP packet, the device updates the existing ARP entry (contained in the cache of the device) 

that matches the received gratuitous ARP packet using the hardware address of the sender carried in 

the gratuitous ARP packet. 

Follow these steps to configure ARP basic functions: 

Enter system view 

system-view 

— 

Add a static ARP entry  

arp static ip-address 
mac-address [ vlan-id 
interface-type interface-number ] 

Optional 

By default, the ARP mapping table is 
empty, and the address mapping 
entries are created dynamically by 
ARP. 

Configure the ARP 
aging timer 

arp timer aging aging-time 

Optional 

By default, the ARP aging timer is 
set to 20 minutes.