2-4.3 Relay - OTS ET42202M-S-PD User Manual

ET42202M-S-PD
L2+ Managed 20-port 100Base-FX/1000Base-X SFP + 4-port 10/100/1000Base-T or
100/1000Base-FX SFP Combo Optical Ethernet Switch with AC + DC inputs

2-4.3 Relay

A DHCP relay agent is used to forward and to transfer DHCP messages between the clients
and the server when they are not in the same subnet domain. It stores the incoming interface
IP address in the GIADDR field of the DHCP packet. The DHCP server can use the value of
GIADDR field to determine the assigned subnet. For such condition, please make sure the
switch configuration of VLAN interface IP address and PVID(Port VLAN ID) correctly.
Web Interface
To configure DHCP Relay in the web interface:
1. Click Configuration, DHCP, Relay
2. Specify the Relay Mode, Relay server, Relay Information Mode, Relay
Information police.
3. Click Apply.
Figure 2-4.3: The DHCP Relay Configuration
Parameter description:
Relay Mode :
Indicates the DHCP relay mode operation.
Possible modes are:
Enabled: Enable DHCP relay mode operation. When DHCP relay mode operation is
enabled, the agent forwards and transfers DHCP messages between the clients
and the server when they are not in the same subnet domain. And the DHCP
broadcast message won't be flooded for security considerations.
Disabled: Disable DHCP relay mode operation.
Relay Server
Indicates the DHCP relay server IP address.
Relay Information Mode
Indicates the DHCP relay information mode option operation. The option 82
circuit ID format as "[vlan_id][module_id][port_no]". The first four characters
represent the VLAN ID, the fifth and sixth characters are the module ID(in
standalone device it always equal 0, in stackable device it means switch ID), and
the last two characters are the port number. For example, "00030108" means the
DHCP message receive form VLAN ID 3, switch ID 1, port No 8. And the option 82
remote ID value is equal the switch MAC address.
Possible modes are:
Enabled: Enable DHCP relay information mode operation. When DHCP relay
information mode operation is enabled, the agent inserts specific information
(option 82) into a DHCP message when forwarding to DHCP server and removes
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