Chapter 1 Dhcp-Snooping Configuration; Dhcp-Snooping Overview; Implementation Of The Dhcp-Snooping Function - Huawei Quidway S3100 Series Operation Manual

Operation Manual – DHCP-Snooping
Quidway S3100 Series Ethernet Switches

Chapter 1 DHCP-Snooping Configuration

1.1 DHCP-Snooping Overview

1.1.1 Implementation of the DHCP-Snooping Function

For security consideration, a network administrator may need to record the IP address
which a user uses to access the network. This helps to check the correspondence
between the IP address obtained from the DHCP server and user host's MAC address.
A Layer 3 switch records user IP address through DHCP relay.
A Layer 2 switch records user IP address by listening DHCP broadcast packets,
which is achieved by employing the DHCP-snooping function.
Figure 1-1 illustrates the diagram of a network with the DHCP-snooping function
implemented. In this network, the DHCP-snooping function is enabled on Switch A, an
S3100 series Ethernet switch.
DHCP Client DHCP Client
DHCP Client DHCP Client
Figure 1-1 Network diagram for DHCP-snooping implementation
Figure 1-2 shows the interaction between a DHCP client and a DHCP server when the
former applies to the latter for an IP address.
DHCP Client DHCP Client
(DHCP-snooping employed) (DHCP-snooping employed)
Ethernet Ethernet Ethernet Ethernet Ethernet Ethernet
DHCP Client DHCP Client
Huawei Technologies Proprietary
Chapter 1 DHCP-Snooping Configuration
Switch A Switch A
- - - -
1-1
Switch B Switch B
(DHCP relay) (DHCP relay)
Internet Internet
Internet Internet
DHCP Server DHCP Server