D-Link DGS-1510 Series Reference Manual page 156

DGS-1510 Series Gigabit Ethernet SmartPro Switch CLI Reference Guide
the relay pool, if the request packet is a relayed packet, the Gateway IP Address (GIADDR) of the
packet is the source of the request. If the GIADDR is zero, the subnet of the received interface is the
source of the packet.
In a DHCP relay pool, the user can further use the class command and the relay target command to
define the relay target address for the request packets that match the option pattern.
Example
This example shows how to a DHCP relay pool, called pool1, is created. In the relay pool, the subnet
172.19.18.0/255.255.255.0 is specified as the source subnet. 10.2.1.1 is specified as the relay
destination address.
Switch# configure terminal
Switch(config)# ip dhcp pool pool1
switch(config-dhcp-pool)# relay source 172.19.18.0 255.255.255.0
switch(config-dhcp-pool)# relay destination 10.2.1.1
switch(config-dhcp-pool)#
17-4 ip dhcp relay information check
This command is used to enable the DHCP relay agent to validate and remove the relay agent
information option in the received DHCP reply packet. Use the no form of this command to globally
disable the check for Option 82.
ip dhcp relay information check
no ip dhcp relay information check
Parameters
None.
Default
By default, this option is disabled.
Command Mode
Global Configuration Mode.
Command Default Level
Level: 12.
Usage Guideline
This command takes effect when the DHCP service is enabled.
The ip dhcp relay information check command and the ip dhcp relay information check-reply
command together determine whether the check function of Option 82 is effective for an interface. If
the ip dhcp relay information check-reply command is not configured for an interface, the global
setting takes effect. If the ip dhcp relay information check-reply command is configured for an
interface, the interface setting takes effect.
When the check for Option 82 of the reply packet is enabled, the device will check the validity of the
Option 82 field in DHCP reply packets it receives from the DHCP server. If the Option 82 field in the
received packet is not present or the option is not the original option inserted by the agent (by
checking the remote ID sub-option, the relay agent drops the packet. Otherwise, the relay agent
removes the Option 82 field and forwards the packet.
If the check is disabled, the packet will be directly forwarded.
Example
This example shows how to enable the global DHCP relay agent check.
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