Publication date: Sept, 2015
Revision A1
28
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 conditions, please make sure the switch configuration of
VLAN interface IP address and PVID (Port VLAN ID) are correct.
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 Policy.
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. 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 is
"[vlan_id][module_id][port_no]". The first four characters represent the VLAN ID, the fifth and
sixth characters are the module ID (in a standalone device it always equals 0, in stackable device it
means switch ID), and the last two characters are the port number. For example, "00030108"
means the DHCP message is received from VLAN ID 3, switch ID 1, port No 8. The option 82 remote
ID value equals 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 a DHCP server and removes it from a DHCP message when transferring to a DHCP
Содержание LPB2910A
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