User manual

xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch
143
Check
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.
DHCP Agent
Information Option 82
Policy
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.
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.
The Implementation of DHCP Information Option 82 in DES-3828P/DES-
3828DC
The config 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:
NOTE: For the circuit ID sub-option of a standalone switch, the module field is
always zero.
Circuit ID sub-option format:
1. 2. 3. 4. 5. 6. 7.
1 6 0 4 VLAN Module Port
1 byte 1 byte 1 byte 1 byte 2 bytes 1 byte 1 byte
a. Sub-option type