Chapter 4 Dhcp Snooping Configuration; Configuring Dhcp Snooping; Introduction To Dhcp Snooping - H3C S7500 Series Operation Manual

Operation Manual – DHCP
H3C S7500 Series Ethernet Switches

Chapter 4 DHCP Snooping Configuration

When configuring DHCP snooping, go to these sections for information you are
interested in:

Configuring DHCP Snooping

DHCP-Snooping Option 82
Displaying and Maintaining DHCP Snooping
DHCP Snooping Configuration Example
4.1 Configuring DHCP Snooping

4.1.1 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.
Layer 3 switches can track DHCP client IP addresses through a DHCP relay
agent.
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 ports can be used to connect DHCP servers or ports of other switches.
Untrusted ports can be used to connect DHCP clients or networks.
Trusted ports forward any received DHCP packet to ensure that DHCP clients can
obtain IP addresses from valid DHCP servers. Untrusted ports drop all the
received packets.
Figure 4-1
Switch A is an S7500 series switch.
illustrates a typical network diagram for DHCP snooping application, where
Chapter 4 DHCP Snooping Configuration
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