Chapter 24 IP Source Guard
GS-2750 User’s Guide
197
24.1.1.3 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
Chapter 29 on page 233
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 (
Chapter 29 on page 233
).
24.1.1.4 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.
24.1.2 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.
Figure 95
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.
A
X
B
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Страница 58: ...Chapter 4 The Web Configurator GS 2750 User s Guide 58 ...
Страница 64: ...Chapter 5 Initial Setup Example GS 2750 User s Guide 64 ...
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Страница 82: ...Chapter 7 Basic Setting GS 2750 User s Guide 82 ...
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Страница 115: ...Chapter 11 Spanning Tree Protocol GS 2750 User s Guide 115 Figure 52 Advanced Application Spanning Tree Protocol MSTP ...
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Страница 134: ...Chapter 15 Link Aggregation GS 2750 User s Guide 134 ...
Страница 144: ...Chapter 17 Port Security GS 2750 User s Guide 144 ...
Страница 155: ...Chapter 19 Policy Rule GS 2750 User s Guide 155 Figure 73 Policy Example example ...
Страница 156: ...Chapter 19 Policy Rule GS 2750 User s Guide 156 ...
Страница 160: ...Chapter 20 Queuing Method GS 2750 User s Guide 160 ...
Страница 166: ...Chapter 21 VLAN Stacking GS 2750 User s Guide 166 ...
Страница 194: ...Chapter 23 Authentication Accounting GS 2750 User s Guide 194 ...
Страница 219: ...219 PART IV IP Application Static Routing 221 RIP 223 Differentiated Services 225 DHCP 233 VRRP 243 ...
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Страница 232: ...Chapter 28 Differentiated Services GS 2750 User s Guide 232 ...
Страница 242: ...Chapter 29 DHCP GS 2750 User s Guide 242 ...
Страница 252: ...Chapter 30 VRRP GS 2750 User s Guide 252 ...
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Страница 278: ...Chapter 32 Access Control GS 2750 User s Guide 278 ...
Страница 280: ...Chapter 33 Diagnostic GS 2750 User s Guide 280 ...
Страница 284: ...Chapter 34 Syslog GS 2750 User s Guide 284 ...
Страница 298: ...Chapter 39 Routing Table GS 2750 User s Guide 298 ...
Страница 301: ...301 PART VI Product Specifications Product Specifications 303 ...
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Страница 309: ...309 PART VII Appendices and Index IP Addresses and Subnetting 311 Legal Information 319 Customer Support 323 Index 329 ...
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Страница 322: ...Appendix B Legal Information GS 2750 User s Guide 322 ...
Страница 328: ...Appendix C Customer Support GS 2750 User s Guide 328 ...