D-Link xstack DES-3810 series Reference Manual page 371

®
xStack
DHCP Relay Agent
Information Option 82
Check
DHCP Relay Agent
Information Option 82
Policy
DHCP Relay Agent
Information Option 82
Remote ID
DHCP Relay Option 60
State
DHCP Relay Option 61
State
Click the Apply button to accept the changes made for each individual section.
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, users may configure a client with the option 82 field. In this situation, disable the
information check feature so that the Switch does not drop the packet. Users may 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.
The Implementation of DHCP Relay Agent Information Option 82
The DHCP Relay Option 82 command configures the DHCP relay agent information option 82 setting of the Switch.
The formats for the circuit ID sub-option and the remote ID sub-option are as follows:
DES-3810 Series Layer 3 Managed Ethernet Switch Web UI Reference Guide
The default is Disabled.
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 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- When 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 Enabled, 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 Relay 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.
Here the user can enter the DHCP Relay Agent Information Option 82 Remote ID.
Here the user can enable or disable the use of the DHCP Relay Option 60 State feature.
Here the user can enable or disable the use of the DHCP Relay Option 61 State feature.
358