D-Link DGS-1250 Emulator - Page 109
ip dhcp relay information check-reply, ip dhcp relay information option
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DGS-1250 Series Gigabit Ethernet Smart Managed Switch CLI Reference Guide 15-5 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 (Optional) Specifies to disable check for Option 82 of the reply packet. Default None. Command Mode Interface Configuration Mode. Usage Guideline This command takes effect when the service dhcp command 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 enable the DHCP relay agent check for the VLAN 100. The effect state of the check function for VLAN 100 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 15-6 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. ip dhcp relay information option no ip dhcp relay information option Parameters None. 106
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