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Chapter 24 IP Source Guard
GS2200-48 User’s Guide
206
24.1.1 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.
24.1.1.1 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: The Switch will drop all DHCP requests if you enable DHCP snooping and there
are no trusted ports.
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.
24.1.1.2 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 GS2200-48
Страница 2: ......
Страница 8: ...Safety Warnings GS2200 48 User s Guide 8 ...
Страница 22: ...22 ...
Страница 28: ...Chapter 1 Getting to Know Your Switch GS2200 48 User s Guide 28 ...
Страница 32: ...Chapter 2 Hardware Installation and Connection GS2200 48 User s Guide 32 ...
Страница 40: ...40 ...
Страница 62: ...Chapter 6 System Status and Port Statistics GS2200 48 User s Guide 62 ...
Страница 76: ...Chapter 7 Basic Setting GS2200 48 User s Guide 76 ...
Страница 78: ...78 ...
Страница 102: ...Chapter 9 Static MAC Forward Setup GS2200 48 User s Guide 102 ...
Страница 122: ...Chapter 11 Spanning Tree Protocol GS2200 48 User s Guide 122 ...
Страница 126: ...Chapter 12 Bandwidth Control GS2200 48 User s Guide 126 ...
Страница 148: ...Chapter 17 Port Security GS2200 48 User s Guide 148 ...
Страница 156: ...Chapter 18 Classifier GS2200 48 User s Guide 156 ...
Страница 164: ...Chapter 19 Policy Rule GS2200 48 User s Guide 164 ...
Страница 214: ...Chapter 24 IP Source Guard GS2200 48 User s Guide 214 Figure 98 DHCP Snooping ...
Страница 235: ...235 PART IV IP Application Static Routing 237 RIP 239 Differentiated Services 241 DHCP 249 VRRP 259 ...
Страница 236: ...236 ...
Страница 270: ...270 ...
Страница 278: ...Chapter 31 Maintenance GS2200 48 User s Guide 278 ...
Страница 304: ...Chapter 34 Syslog GS2200 48 User s Guide 304 ...
Страница 312: ...Chapter 35 Cluster Management GS2200 48 User s Guide 312 ...
Страница 316: ...Chapter 36 MAC Table GS2200 48 User s Guide 316 ...
Страница 320: ...Chapter 37 IP Table GS2200 48 User s Guide 320 ...
Страница 324: ...Chapter 39 Routing Table GS2200 48 User s Guide 324 ...
Страница 327: ...327 PART VI Product Specifications Product Specifications 329 ...
Страница 328: ...328 ...
Страница 336: ...Chapter 41 Product Specifications GS2200 48 User s Guide 336 ...
Страница 337: ...337 PART VII Appendices and Index IP Addresses and Subnetting 339 Legal Information 349 Index 353 ...
Страница 338: ...338 ...
Страница 352: ...Appendix B Legal Information GS2200 48 User s Guide 352 ...
Страница 362: ...Index GS2200 48 User s Guide 362 ...