Displaying And Maintaining Dhcp Snooping; Dhcp Snooping Configuration Example - 3Com Switch 4800G 24-Port Configuration Manual

Displaying and
Maintaining DHCP
Snooping
DHCP Snooping
Configuration
Example
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.
To do...
Display DHCP snooping address
binding information
Display information about trusted
ports
Clear DHCP snooping address
binding information
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
Switch A
DHCP server
GE1/0/1
DHCP snooping
GE1/0/2 GE 1/0 /3
DHCP client DHCP client
Configuration procedure
# Enable DHCP snooping.
<SwitchB> system-view
[SwitchB] dhcp-snooping

Displaying and Maintaining DHCP Snooping

Use the command...
display dhcp-snooping
display dhcp-snooping trust
reset dhcp-snooping { all | ip
ip-address }
Switch B
829
Remarks
Available in any view
Available in user view