Chapter 26 IP Source Guard
XS1920 Series User’s Guide
251
Figure 171
Example: Man-in-the-middle Attack
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.
26.15.2.1 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.
• They appear only in the
ARP Inspection
screens, not in the
MAC Address Filter
screens.
26.15.2.2 Trusted vs. Untrusted Ports
Every port is either a trusted port or an untrusted port for ARP inspection. This setting is
independent of the trusted/untrusted setting for DHCP snooping. You can also specify the maximum
rate at which the Switch receives ARP packets on untrusted ports.
The Switch does not discard ARP packets on trusted ports for any reason.
The Switch discards ARP packets on untrusted ports in the following situations:
• The sender’s information in the ARP packet does not match any of the current bindings.
• The rate at which ARP packets arrive is too high.
26.15.2.3 Syslog
The Switch can send syslog messages to the specified syslog server (
when it forwards or discards ARP packets. The Switch can consolidate log messages and send log
messages in batches to make this mechanism more efficient.
A
X
B
Содержание XS1920 Series
Страница 18: ...18 PART I User s Guide ...
Страница 32: ...32 PART II Technical Reference ...
Страница 171: ...Chapter 21 Classifier XS1920 Series User s Guide 171 Figure 119 Advanced Application Classifier Configuration ...
Страница 177: ...Chapter 21 Classifier XS1920 Series User s Guide 177 Figure 122 Classifier Example EXAMPLE ...
Страница 209: ...Chapter 24 Multicast XS1920 Series User s Guide 209 Figure 143 MVR Group Configuration Example EXAMPLE ...
Страница 383: ...Chapter 50 Configure Clone XS1920 Series User s Guide 383 Figure 273 Management Configure Clone ...
Страница 408: ...Appendix C IPv6 XS1920 Series User s Guide 408 ...
Страница 412: ...Appendix D Legal Information XS1920 Series User s Guide 412 Environmental Product Declaration ...