Technical Reference; Arp Inspection Overview - ZyXEL Communications XMG1930-30 User Manual

Table 309 SECURITY > IPv6 Source Guard > DHCPv6 Trust Setup (continued)
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75.15 Technical Reference

This section provides technical background information on the topics discussed in this chapter.

75.15.1 ARP Inspection Overview

Use ARP inspection to filter unauthorized ARP packets on the network. This can prevent many kinds of
man-in-the-middle attacks, such as the one in the following example.
Figure 391
In this example, computer B tries to establish a connection with computer A. Computer X is in the same
broadcast domain as computer A and intercepts the ARP request for computer A. Then, computer X
does the following things:
• It pretends to be computer A and responds to computer B.
• It pretends to be computer B and sends a message to computer A.
As a result, all the communication between computer A and computer B passes through computer X.
Computer X can read and alter the information passed between them.
75.15.1.1 ARP Inspection and MAC Address Filters
When the Switch identifies an unauthorized ARP packet, it automatically creates a MAC address filter to
block traffic from the source MAC address and source VLAN ID of the unauthorized ARP packet. You
can configure how long the MAC address filter remains in the Switch.
These MAC address filters are different than regular MAC address filters.
• They are stored only in volatile memory.
• They do not use the same space in memory that regular MAC address filters use.
Chapter 75 ARP Inspection
DESCRIPTION
Click Apply to save your changes to the Switch's run-time memory. The Switch loses these
changes if it is turned off or loses power, so use the Save link on the top navigation panel to
save your changes to the non-volatile memory when you are done configuring.
Click this to reset the values in this screen to their last-saved values.
Example: Man-in-the-middle Attack
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