Operation Manual – DHCPH3C S5500-EI Series Ethernet Switches Chapter 5 DHCP Snooping Configuration5-6Note:z To support Option 82, it is required to perform related configuration on both theDHCP server and the device enabled with DHCP Snooping. Refer to Configuringthe Handling Mode for Option 82 for DHCP server configuration of this kind.z If the handling strategy of the DHCP-Snooping-enabled device is configured asreplace, you need to configure a padding format for Option 82. If the handlingstrategy is keep or drop, you need not configure any padding format.z If the Option 82 is padded with the device name (sysname) of a node, the devicename must contain no spaces. Otherwise, the DHCP-Snooping-enabled device willdrop the message.5.4 Displaying and Maintaining DHCP SnoopingTo do… Use the command… RemarksDisplay DHCP snoopingaddress binding information display dhcp-snoopingDisplay information abouttrusted portsdisplay dhcp-snoopingtrustAvailable in anyviewClear DHCP snoopingaddress binding informationreset dhcp-snooping { all |ip ip-address }Available in userview5.5 DHCP Snooping Configuration ExampleI. Network requirementsz Switch B is connected to a DHCP server through GigabitEthernet 1/0/1, and to twoDHCP clients through GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3.z GigabitEthernet 1/0/1 forwards DHCP server responses while the other two donot.z Switch B records clients’ IP-to-MAC address bindings in DHCP-REQUESTmessages and DHCP-ACK messages received from trusted ports.z Switch B supports Option 82. After receiving a DHCP request from the client,Switch B adds Option 82 padded in verbose format to the request message andforwards the message to the DHCP server.
