3Com 4800G Series, Configuration Manual

Page: 829 / 1246

Displaying and Maintaining DHCP Snooping 829
■
If the handling strategy of the DHCP-Snooping-enabled device is configured as
replace , you need to configure a padding format for Option 82. If the
handling strategy is keep or drop , you need not configure any padding
format.
■
If the Option 82 is padded with the device name (sysname) of a node, the
device name must contain no spaces. Otherwise, the DHCP-Snooping-enabled
device will drop the message.
Displaying and
Maintaining DHCP
Snooping
DHCP Snooping
Configuration
Example
Network requirements
■
Switch B is connected to a DHCP server through GigabitEthernet 1/0/1, and to
two DHCP clients through GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3.
■
GigabitEthernet 1/0/1 forwards DHCP server responses while the other two do
not.
■
Switch B records clients’ IP-to-MAC address bindings in DHCP-REQUEST
messages and DHCP-ACK messages received from trusted ports.
■
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 and
forwards the message to the DHCP server.
Network diagram
Figure 252 Network diagram for DHCP snooping configuration
Configuration procedure
# Enable DHCP snooping.
<SwitchB> system-view
[SwitchB] dhcp-snooping
To do… Use the command… Remarks
Display DHCP snooping address
binding information display dhcp-snooping Available in any view
Display information about trusted
ports display dhcp-snooping trust
Clear DHCP snooping address
binding information reset dhcp-snooping { all | ip
ip-address }
Available in user view
GE1/0/1
Switch A
DHCP server
Switch B
DHCP snooping
GE1/0/2
DHCP client DHCP client
GE 1/0 /3