Chapter
3: Web Management
DHCP - Relay
PoE Switch User Manual | 46
3.1.4.3. DHCP - 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.
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 it from a DHCP
message when transferring to DHCP client. It only works when DHCP relay operation
mode is enabled.
