Dhcp | Relay - Comtrol RocketLinx MP1204-XT User Manual

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 that the switch configuration of VLAN interface IP address and
PVID (Port VLAN ID) are correct.
Item
Indicates the DHCP relay mode operation.
Possible modes are:
• Enabled: Enable the DHCP relay mode operation. When DHCP relay mode operation
Relay Mode
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 is not be flooded for security considerations.
• Disabled: Disable DHCP relay mode operation.
Relay Server Indicates the DHCP relay server IP address.
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 (0), and the last two characters are
the port number. For example, 00030108 means that the DHCP message was received
from VLAN ID 3, switch ID 1, port No The Option 82 remote ID value is equal the
switch MAC address.
Relay
Possible modes are:
Information
Mode
• Enabled: Enable the 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.
• Disabled: Disable DHCP relay information mode operation.
Indicates the DHCP relay information option policy. When DHCP relay information
mode operation is enabled, if the agent receives a DHCP message that already contains
relay agent information it enforces the policy. The Replace policy is invalid when relay
information mode is disabled. Possible policies are:
Relay
• Replace: Replaces the original relay information when a DHCP message that already
Information
contains it is received.
Policy
• Keep: Keeps the original relay information when a DHCP message that already
contains it is received.
• Drop: Drops the package when a DHCP message that already contains relay
information is received.
RocketLinx MP1204-XT User Guide: 2000644 Rev. A
Configuration | DHCP | Relay
DHCP | Relay
Configuration Pages - 53