Port:
Displays the port number.
Trusted Port:
Select Enable/Disable the port to be a Trusted Port. Only the
Trusted Port can receive the DHCP packets from DHCP
servers.
Rate Limit:
Select the value to specify the maximum amount of DHCP
messages that can be forwarded by the switch of this port
per second. The excessive DHCP packets will be discarded.
Circuit ID Customization:
Enable or Disable the switch to define Circuit ID.
Circuit ID:
Enter the sub-option Circuit ID for the customized Option 82.
LAG:
Displays the LAG to which the port belongs to.
14.3
ARP Inspection
Since ARP protocol is implemented with the premise that all the Hosts and Gateways are
trusted, there are high security risks during ARP Implementation Procedure in the actual
complex network. Thus, the cheating attacks against ARP, such as imitating Gateway, cheating
Gateway, cheating terminal Hosts and ARP Flooding Attack, frequently occur to the network,
especially to the large network such as campus network and so on. The following part will
simply introduce these ARP attacks.
Imitating Gateway
The attacker sends the MAC address of a forged Gateway to Host, and then the Host will
automatically update the ARP table after receiving the ARP response packets, which causes
that the Host cannot access the network normally. The ARP Attack implemented by imitating
Gateway is illustrated in the following figure.
Figure 14-8 ARP Attack - Imitating Gateway
As the above figure shown, the attacker sends the fake ARP packets with a forged Gateway
address to the normal Host, and then the Host will automatically update the ARP table after
receiving the ARP packets. When the Host tries to communicate with Gateway, the Host will
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