User Manual

User’s Manual of LRP-822CS/LRP-1622CS
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4.9.7.8 Option 82 Global Setting
DHCP pr relay mechanism for ation about the switch and its DHCP clients to DHCP servers. Known as
, it allows compatible when assigning IP addresses, or to set other
for clients. It is also ng malicious network attacks from attached clients on DHCP
services, such as IP Spoofing, Client Identifier Spoofing, MAC Address Spoofing, and Address Exhaustion.
The DHCP option 82 enables a DHCP ation into a DHCP request packets when forwarding
ient DHCP packets to a DHCP server and remove the specific information from a DHCP reply packets when forwarding server
s to a DHCP client. The DHCP server can use this information to implement IP address or other assignment
policies. Spe by setting two sub-options:
 Circuit ID (option 1)
 Remote ID (option 2)
The Circuit ID sub-option is supposed to include information specific to which circuit the request came in on.
The Remote ID sub-option was designed to carry information relating to the remote host end of the circuit.
The definition of Circuit ID in the switch is 4 bytes in length and the format is "vlan_id" "module_id" "port_no". The parameter of
"vlan_id" is the first two bytes represent the VLAN ID. The parameter of "module_id" is the third byte for the module ID (in
standalone switch it always equal 0, in switch it means switch ID). The parameter of "port_no" is the fourth byte and it means
the port number.
After enabling DHCP snooping, the switch will monitor all the DHCP messages and implement software transmission. The
DHCP Rate Limit Setting and Config screens in Figure 4-9-44 & Figure 4-9-45 appear.
ovides a sending inform
DHCP Option 82 DHCP servers to use the information
services or policies an effective tool in preventi
relay agent to insert specific inform
cl
DHCP packet
cifically the option works
Figure 4-9-44 Option 82 Global Setting Page Screenshot
The page includes the following fields:
Object Description
 State
Set the option 2 (remote ID option) content of option 82 added by DHCP request
packets.
lt VLAN MAC format.
 User-Define means the remote-id content of option 82 specified by users
 Default means the defau