User's Manual

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Chapter 23 ARP Scanning Prevention
Function Configuration
23.1 Introduction to ARP Scanning Prevention Function
ARP scanning is a common method of network attack. In order to detect all the active hosts in a network
segment, the attack source will broadcast lots of ARP messages in the segment, which will take up a large
part of the bandwidth of the network. It might even do large-traffic-attack in the network via fake ARP
messages to collapse of the network by exhausting the bandwidth. Usually ARP scanning is just a preface of
other more dangerous attack methods, such as automatic virus infection or the ensuing port scanning,
vulnerability scanning aiming at stealing information, distorted message attack, and DOS attack, etc.
Since ARP scanning threatens the security and stability of the network with great danger, so it is very
significant to prevent it. Switch provides a complete resolution to prevent ARP scanning: if there is any host or
port with ARP scanning features is found in the segment, the switch will cut off the attack source to ensure the
security of the network.
There are two methods to prevent ARP scanning: port-based and IP-based. The port-based ARP scanning
will count the number to ARP messages received from a port in a certain time range, if the number is larger
than a preset threshold, this port will be “down”. The IP-based ARP scanning will count the number to ARP
messages received from an IP in the segment in a certain time range, if the number is larger than a preset
threshold, any traffic from this IP will be blocked, while the port related with this IP will not be “down”. These
two methods can be enabled simultaneously. After a port or an IP is disabled, users can recover its state via
automatic recovery function.
To improve the effect of the switch, users can configure trusted ports and IP, the ARP messages from which
will not be checked by the switch. Thus the load of the switch can be effectively decreased.
23.2 ARP Scanning Prevention Configuration Task Sequence
1． Enable the ARP Scanning Prevention function.
2． Configure the threshold of the port-based and IP-based ARP Scanning Prevention
3． Configure trusted ports
4． Configure trusted IP
5． Configure automatic recovery time
6． Display relative information of debug information and ARP scanning