41-1
41
DHCP Snooping Configuration
When configuring DHCP snooping, go to these sections for information you are interested in:
z
DHCP Snooping Overview
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Configuring DHCP Snooping
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Displaying and Maintaining DHCP Snooping Configuration
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DHCP Snooping Configuration Examples
P Snooping Overview
DHC
Introd
adm
tionship between the IP addresses the DHCP clients
obtained from DHCP servers and the MAC addresses of the DHCP clients.
ts’ IP addresses through the DHCP snooping function at the data
link layer.
ay obtains an illegal IP
servers, you can
y the DHCP snooping function.
ctly or indirectly. It forwards
s.
he DHCP-ACK or
DHCP clients from
receiving invalid IP addresses.
uction to DHCP Snooping
For the sake of security, the IP addresses used by online DHCP clients need to be tracked for the
inistrator to verify the corresponding rela
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Switches can track DHCP clients’ IP addresses through the security function of the DHCP relay
agent operating at the network layer.
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Switches can track DHCP clien
When an unauthorized DHCP server exists in the network, a DHCP client m
address. To ensure that the DHCP clients obtain IP addresses from valid DHCP
specify a port to be a trusted port or an untrusted port b
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Trusted: A trusted port is connected to an authorized DHCP server dire
DHCP messages to guarantee that DHCP clients can obtain valid IP addresse
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Untrusted: An untrusted port is connected to an unauthorized DHCP server. T
DHCP-OFFER packets received from the port are discarded, preventing
Figure 41-1
illustrates a typical network diagram for DHCP snooping application, where Switch A is an
S4500 series Ethernet switch.