59
DHCP S
NOOPING
C
ONFIGURATION
Configuring DHCP
Snooping
Introduction to DHCP
Snooping
For the sake of security, the IP addresses used by online DHCP clients need to be
tracked for the administrator to verify the corresponding relationship between the
IP addresses the DHCP clients obtained from DHCP servers and the MAC addresses
of the DHCP clients.
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Layer 3 switches can track DHCP client IP addresses through a DHCP relay
agent.
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Layer 2 switches can track DHCP client IP addresses through the DHCP
snooping function, which listens to DHCP broadcast packets.
When an unauthorized DHCP server exists in the network, a DHCP client may
obtain an illegal IP address. To ensure that the DHCP clients obtain IP addresses
from valid DHCP servers, you can specify a port to be a trusted port or an
untrusted port through the DHCP snooping function.
■
Trusted: A trusted port is connected to an authorized DHCP server directly or
indirectly. It forwards DHCP messages to guarantee that DHCP clients can
obtain valid IP addresses.
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Untrusted: An untrusted port is connected to an unauthorized DHCP server.
The DHCP-ACK or DHCP-OFFER packets received from the port are discarded,
preventing DHCP clients from receiving invalid IP addresses.
Figure 157 illustrates a typical network diagram for DHCP snooping application,
where Switch A is a Switch 7750.
Содержание Switch 7754
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Страница 70: ...70 CHAPTER 5 LOGGING IN USING MODEM ...
Страница 76: ...76 CHAPTER 7 LOGGING IN THROUGH NMS ...
Страница 86: ...86 CHAPTER 9 CONFIGURATION FILE MANAGEMENT ...
Страница 120: ...120 CHAPTER 13 ISOLATE USER VLAN CONFIGURATION ...
Страница 126: ...126 CHAPTER 14 SUPER VLAN ...
Страница 136: ...136 CHAPTER 16 IP PERFORMANCE CONFIGURATION ...
Страница 152: ...152 CHAPTER 17 IPX CONFIGURATION ...
Страница 164: ...164 CHAPTER 19 QINQ CONFIGURATION ...
Страница 172: ...172 CHAPTER 21 SHARED VLAN CONFIGURATION ...
Страница 182: ...182 CHAPTER 22 PORT BASIC CONFIGURATION ...
Страница 198: ...198 CHAPTER 24 PORT ISOLATION CONFIGURATION ...
Страница 208: ...208 CHAPTER 25 PORT SECURITY CONFIGURATION ...
Страница 224: ...224 CHAPTER 27 DLDP CONFIGURATION ...
Страница 232: ...232 CHAPTER 28 MAC ADDRESS TABLE MANAGEMENT ...
Страница 240: ...240 CHAPTER 29 CENTRALIZED MAC ADDRESS AUTHENTICATION CONFIGURATION ...
Страница 280: ...280 CHAPTER 30 MSTP CONFIGURATION ...
Страница 348: ...348 CHAPTER 35 IS IS CONFIGURATION ...
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Страница 412: ...412 CHAPTER 40 HABP CONFIGURATION ...
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Страница 426: ...426 CHAPTER 42 GMRP CONFIGURATION ...
Страница 480: ...480 CHAPTER 47 PIM CONFIGURATION ...
Страница 506: ...506 CHAPTER 48 MSDP CONFIGURATION ...
Страница 552: ...552 CHAPTER 51 TRAFFIC ACCOUNTING CONFIGURATION ...
Страница 570: ...570 CHAPTER 53 HA CONFIGURATION ...
Страница 582: ...582 CHAPTER 54 ARP CONFIGURATION SwitchA arp protective down recover interval 200 ...
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