3com 2928 User Guide

 

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Select the Advanced Options checkbox. 

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Type 100 for VLAN ID. 

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Select GigabitEthernet1/0/1 for Port. 

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Click Apply to complete the configuration. 

In a gratuitous ARP packet, the sender IP address and the target IP address are both the IP address of 
the device issuing the packet, the sender MAC address is the MAC address of the device, and the target 
MAC address is the broadcast address ff:ff:ff:ff:ff:ff. 
A device implements the following functions by sending gratuitous ARP packets: 

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Determining whether its IP address is already used by another device. 

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Informing other devices about the change of its MAC address so that they can update their ARP 
entries. 

A device receiving a gratuitous ARP packet adds the information carried in the packet to its own 
dynamic ARP table if it finds no corresponding ARP entry exists in the cache. 
An attacker sends spoofed gratuitous ARP packets to hosts on a network. As a result, traffic that the 
hosts want to send to the gateway is sent to the attacker instead, and the hosts cannot access external 
networks. To prevent such gateway spoofing attacks, you can enable the gateway to send gratuitous 
ARP packets periodically. In this way, each host can learn correct gateway address information. 

Select Network > ARP Management from the navigation tree, and click the Gratuitous ARP tab to 
enter the page shown in 

Gratuitous ARP configuration page 

 

 

 describes the gratuitous ARP configuration items.