Chapter 26 IP Source Guard
XS1920 Series User’s Guide
250
Figure 170
DHCP Snooping Database File Format
The <initial-checksum> helps distinguish between the bindings in the latest update and the
bindings from previous updates. Each binding consists of 72 bytes, a space, and another checksum
that is used to validate the binding when it is read. If the calculated checksum is not equal to the
checksum in the file, that binding and all others after it are ignored.
26.15.1.3 DHCP Relay Option 82 Information
The Switch can add information to DHCP requests that it does not discard. This provides the DHCP
server more information about the source of the requests. The Switch can add the following
information:
• Slot ID (1 byte), port ID (1 byte), and source VLAN ID (2 bytes)
• System name (up to 32 bytes)
This information is stored in an Agent Information field in the option 82 field of the DHCP headers of
client DHCP request frames. See
for more information about DHCP relay
option 82.
When the DHCP server responds, the Switch removes the information in the Agent Information field
before forwarding the response to the original source.
You can configure this setting for each source VLAN. This setting is independent of the DHCP relay
settings (
).
26.15.1.4 Configuring DHCP Snooping
Follow these steps to configure DHCP snooping on the Switch.
1
Enable DHCP snooping on the Switch.
2
Enable DHCP snooping on each VLAN, and configure DHCP relay option 82.
3
Configure trusted and untrusted ports, and specify the maximum number of DHCP packets that
each port can receive per second.
4
Configure static bindings.
26.15.2 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.
<initial-checksum>
TYPE DHCP-SNOOPING
VERSION 1
BEGIN
<binding-1> <checksum-1>
<binding-2> <checksum-1-2>
...
...
<binding-n> <checksum-1-2-..-n>
END
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 ...