INS_CNXE2GE2TX8MSPOE 11 Jan 2021 PAGE 68
INSTALLATION AND OPERATION MANUAL
CNXE2GE2TX8MSPOE
TECH SUPPORT: 1.888.678.9427
6.2.2 DHCP Relay
DHCP relay is used to forward and transfer DHCP messages between the clients and the server
when they are not in the same subnet domain. You can configure the function in this page.
Label
Description
Relay Mode
Indicates the existing DHCP relay mode. The modes include: Enabled: activate DHCP
relay. When DHCP relay is enabled, the agent forwards and transfers DHCP messages
between the clients and the server when they are not in the same subnet domain to
prevent the DHCP broadcast message from flooding for security considerations.
Disabled: disable DHCP relay
Relay Server
Indicates the DHCP relay server IP address. A DHCP relay agent is used to forward and
transfer DHCP messages between the clients and the server when they are not in the
same subnet domain.
Relay
Information
Mode
Indicates the existing DHCP relay information mode. The format of DHCP option 82
circuit ID format is “[vlan_id][module_id][port_no]”. The first four characters represent
the VLAN ID, and the fifth and sixth characters are the module ID. In stand-alone
devices, the module ID always equals to 0; in stacked devices, it means switch ID. The
last two characters are the port number. For example, “00030108” means the DHCP
message received form VLAN ID 3, switch ID 1, and port No. 8. The option 82 remote ID
value equals to the switch MAC address.
The modes include:
Enabled: activate DHCP relay information. When DHCP relay information is enabled, the
agent inserts specific information (option 82) into a DHCP message when forwarding
to a DHCP server and removes it from a DHCP message when transferring to a DHCP
client. It only works when DHCP relay mode is enabled.
Disabled: disable DHCP relay information
Relay
Information
Policy
Indicates the policies to be enforced when receiving DHCP relay information. When
DHCP relay information mode is enabled, if the agent receives a DHCP message that
already contains relay agent information, it will enforce the policy. The Replace option is
invalid when relay information mode is disabled. The policies includes: Replace: replace
the original relay information when a DHCP message containing the information is
received.
Keep: keep the original relay information when a DHCP message containing the
information is received.
Drop: drop the package when a DHCP message containing the information is received.
