Chapter 26 IP Source Guard
MGS3700-12C User’s Guide
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26.1.1 DHCP Snooping Overview
Use DHCP snooping to filter unauthorized DHCP packets on the network and to
build the binding table dynamically. This can prevent clients from getting IP
addresses from unauthorized DHCP servers.
26.1.1.1 Trusted vs. Untrusted Ports
Every port is either a trusted port or an untrusted port for DHCP snooping. This
setting is independent of the trusted/untrusted setting for ARP inspection. You can
also specify the maximum number for DHCP packets that each port (trusted or
untrusted) can receive each second.
Trusted ports are connected to DHCP servers or other switches. The Switch
discards DHCP packets from trusted ports only if the rate at which DHCP packets
arrive is too high. The Switch learns dynamic bindings from trusted ports.
Note: If DHCP is enabled and there are no trusted ports, DHCP requests will not
succeed.
Untrusted ports are connected to subscribers. The Switch discards DHCP packets
from untrusted ports in the following situations:
• The packet is a DHCP server packet (for example, OFFER, ACK, or NACK).
• The source MAC address and source IP address in the packet do not match any
of the current bindings.
• The packet is a RELEASE or DECLINE packet, and the source MAC address and
source port do not match any of the current bindings.
• The rate at which DHCP packets arrive is too high.
26.1.1.2 DHCP Snooping Database
The Switch stores the binding table in volatile memory. If the Switch restarts, it
loads static bindings from permanent memory but loses the dynamic bindings, in
which case the devices in the network have to send DHCP requests again. As a
result, it is recommended you configure the DHCP snooping database.
The DHCP snooping database maintains the dynamic bindings for DHCP snooping
and ARP inspection in a file on an external TFTP server. If you set up the DHCP
snooping database, the Switch can reload the dynamic bindings from the DHCP
snooping database after the Switch restarts.
Содержание MGS3700-12C
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Страница 8: ...Safety Warnings MGS3700 12C User s Guide 8 ...
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Страница 30: ...Chapter 1 Getting to Know Your Switch MGS3700 12C User s Guide 30 ...
Страница 46: ...Chapter 3 Hardware Overview MGS3700 12C User s Guide 46 ...
Страница 56: ...Chapter 4 The Web Configurator MGS3700 12C User s Guide 56 ...
Страница 62: ...Chapter 5 Initial Setup Example MGS3700 12C User s Guide 62 ...
Страница 90: ...Chapter 6 Tutorials MGS3700 12C User s Guide 90 ...
Страница 91: ...91 PART II Basic Configuration System Status and Port Statistics 93 Basic Setting 99 ...
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Страница 114: ...Chapter 8 Basic Setting MGS3700 12C User s Guide 114 ...
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Страница 136: ...Chapter 9 VLAN MGS3700 12C User s Guide 136 ...
Страница 140: ...Chapter 10 Static MAC Forward Setup MGS3700 12C User s Guide 140 ...
Страница 172: ...Chapter 14 Bandwidth Control MGS3700 12C User s Guide 172 ...
Страница 204: ...Chapter 18 MGS3700 12C User s Guide 204 ...
Страница 210: ...Chapter 19 Port Security MGS3700 12C User s Guide 210 ...
Страница 218: ...Chapter 20 Classifier MGS3700 12C User s Guide 218 ...
Страница 226: ...Chapter 21 Policy Rule MGS3700 12C User s Guide 226 ...
Страница 294: ...Chapter 26 IP Source Guard MGS3700 12C User s Guide 294 ...
Страница 316: ...Chapter 31 Error Diable MGS3700 12C User s Guide 316 ...
Страница 330: ...Chapter 33 Private VLAN MGS3700 12C User s Guide 330 ...
Страница 334: ...Chapter 34 Green Ethernet MGS3700 12C User s Guide 334 ...
Страница 335: ...335 PART IV IP Application Static Route 337 Differentiated Services 341 DHCP 349 ...
Страница 336: ...336 ...
Страница 340: ...Chapter 35 Static Route MGS3700 12C User s Guide 340 ...
Страница 356: ...Chapter 37 DHCP MGS3700 12C User s Guide 356 ...
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Страница 366: ...Chapter 38 Maintenance MGS3700 12C User s Guide 366 ...
Страница 388: ...Chapter 39 Access Control MGS3700 12C User s Guide 388 ...
Страница 394: ...Chapter 41 Syslog MGS3700 12C User s Guide 394 ...
Страница 402: ...Chapter 42 Cluster Management MGS3700 12C User s Guide 402 ...
Страница 406: ...Chapter 43 MAC Table MGS3700 12C User s Guide 406 ...
Страница 411: ...Chapter 45 Configure Clone MGS3700 12C User s Guide 411 ...
Страница 412: ...Chapter 45 Configure Clone MGS3700 12C User s Guide 412 ...
Страница 413: ...413 PART VI Troubleshooting Product Specifications Troubleshooting 415 Product Specifications 419 ...
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Страница 428: ...Chapter 47 Product Specifications MGS3700 12C User s Guide 428 ...
Страница 429: ...429 PART VII Appendices and Index Common Services 431 Legal Information 435 Index 417 ...
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Страница 434: ...Appendix A Common Services MGS3700 12C User s Guide 434 ...
Страница 438: ...Appendix B Legal Information MGS3700 12C User s Guide 438 ...