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DGS-1510 Series Gigabit Ethernet SmartPro Switch CLI Reference Guide
Switch# configure terminal
Switch(config)# ip dhcp relay information check
switch(config)#
17-5
ip dhcp relay information check-reply
This command is used to configure the DHCP relay agent to validate the relay agent information
option in the received DHCP reply packet. Use the no form of this command to remove the
configuration for the interface.
ip dhcp relay information check-reply [none]
no ip dhcp relay information check-reply [none]
Parameters
none
Default
None.
Command Mode
Interface Configuration Mode.
Command Default Level
Level: 12.
Usage Guideline
This command only 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 disable the global DHCP relay agent check but enables the DHCP relay
agent check for the VLAN 100. The effect state of the check function for VLAN100 is enabled.
Switch# configure terminal
Switch(config)# no ip dhcp relay information check
switch(config)# interface vlan 100
switch(config-if)# ip dhcp relay information check-reply
17-6
ip dhcp relay information option
This command is used to enable the insertion of relay agent information (Option 82) during the relay
of DHCP request packets. Use the no form of this command to disable this insert function.
(Optional) Specifies to disable check for Option 82 of the reply
packet.
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