D-Link DES-3526 - Switch - Stackable User Manual page 151

xStack
DHCP Agent
Information Option 82
Check
DHCP Agent
Information Option 82
Policy
DHCP Agent
Information Option 82
Remote ID
Click Apply to implement any changes that have been made.
NOTE: If the Switch receives a packet that contains the option-82 field from a DHCP client and the
information-checking feature is enabled, the switch drops the packet because it is invalid. However, in
some instances, you might configure a client with the option-82 field. In this situation, you should
disable the information-check feature so that the switch does not remove the option-82 field from the
packet. You can configure the action that the switch takes when it receives a packet with existing
option-82 information by configuring the DHCP Agent Information Option 82 Policy.
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DES-3500 Series Layer 2 Stackable Fast Ethernet Managed Switch User Manual
Enabled –When this field is toggled to Enabled the relay agent will insert and remove DHCP
relay information (option 82 field) in messages between DHCP servers and clients. When
the relay agent receives the DHCP request, it adds the option 82 information, and the IP
address of the relay agent (if the relay agent is configured), to the packet. Once the option
82 information has been added to the packet it is sent on to the DHCP server. When the
DHCP server receives the packet, if the server is capable of option 82, it can implement
policies like restricting the number of IP addresses that can be assigned to a single remote
ID or circuit ID. Then the DHCP server echoes the option 82 field in the DHCP reply. The
DHCP server unicasts the reply to the back to the relay agent if the request was relayed to
the server by the relay agent. The switch verifies that it originally inserted the option 82
data. Finally, the relay agent removes the option 82 field and forwards the packet to the
switch port that connects to the DHCP client that sent the DHCP request.
Disabled- If the field is toggled to Disabled the relay agent will not insert and remove DHCP
relay information (option 82 field) in messages between DHCP servers and clients, and the
check and policy settings will have no effect.
This field can be toggled between Enabled and Disabled using the pull-down menu. It is
used to enable or disable the Switches ability to check the validity of the packet's option 82
field.
Enabled– When the field is toggled to Enable, the relay agent will check the validity of the
packet's option 82 field. If the switch receives a packet that contains the option-82 field from
a DHCP client, the switch drops the packet because it is invalid. In packets received from
DHCP servers, the relay agent will drop invalid messages.
Disabled- When the field is toggled to Disabled, the relay agent will not check the validity of
the packet's option 82 field.
This field can be toggled between Replace, Drop, and Keep by using the pull-down menu.
It is used to set the Switches policy for handling packets when the DHCP Agent
Information Option 82 Check is set to Disabled. The default is Replace.
Replace- The option 82 field will be replaced if the option 82 field already exists in the
packet received from the DHCP client.
Drop- The packet will be dropped if the option 82 field already exists in the packet received
from the DHCP client.
Keep-The option 82 field will be retained if the option 82 field already exists in the packet
received from the DHCP client.
This field specifies the feature which allows the user to configure the Remote ID as any
specific string. When the Remote ID state is set to Default, the switch's system MAC
address is used as the Remote ID. When the Remote ID state is configured to be user-
defined, the user-defined string is used as the Remote ID.
Note: The maximum number of characters that can be used is 32.
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