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ROS™ v3.5 48 RS400
1.14 DHCP Relay Agent (N/A for RMC30)
DHCP Relay Agent is a device that forwards DHCP packets between clients and servers when
they are not on the same physical LAN segment or IP Subnet. The feature is enabled if DHCP
Server IP address and set of access ports are configured.
DHCP Option 82 provides a mechanism for assigning IP Address based on location of the client
device is in the network. Information about client’s location can be sent along with the DHCP
request to the server. The DHCP server makes a decision about IP Address to be assigned,
based on this information.
DHCP Relay Agent takes the broadcast DHCP requests from clients received on configured
access port and inserts the relay agent information option (option 82) in the packet. The option
82 contains the VLAN (2 bytes) and the port number of access port (2 bytes) (the circuit ID sub-
option) and switch’s MAC address (the remote ID sub-option). These information uniquely
define access port’s position in the network.
DHCP Server supporting DHCP option 82 sends unicast reply and echoes option 82. The
DHCP Relay Agent removes option 82 field and broadcasts the packet to the port from which
the original request was received.
These parameters provide ability to configure switch to act as Relay Agent for DHCP Option 82.
DHCP Relay Agent is communicating to the server on management interface. The agent’s IP
address is the address configured for the management interface.
Figure 24: DHCP Relay Agent Form
DHCP Server Address
Synopsis: ###.###.###.### where ### ranges from 0 to 255
Default:
This parameter specifies the IP address of the DHCP server to which DHCP queries will be
forwarded from this Relay Agent.