UMN:CLI User ManualV5812G284Before configuring DHCP server or relay, you need to use the service dhcp commandfirst to activate the DHCP function in the system.8.6.4.1 DHCP Helper AddressA DHCP client sends DHCP_DISCOVER message to a DHCP server. DHCP_DISCOVERmessage is broadcasted within the network to which it is attached. If the client is on anetwork that does not have any DHCP server, the broadcast is not forwarded becausethe switch is configured to not forward broadcast traffic. To solve this problem, you canconfigure the interface that is receiving the broadcasts to forward certain classes ofbroadcast to a helper address.To specify a DHCP helper address, use the following command.Command Mode Descriptionip dhcp helper-address A.B.C.DInterfaceSpecifies a DHCP helper address. More than oneaddress is possible.A.B.C.D: DHCP server addressno ip dhcp helper-address{A.B.C.D | all} Deletes a specified packet forwarding address.If a DHCP helper address is specified on an interface, the V5812G will enable a DHCPrelay agent.You can also specify an organizationally unique identifier (OUI) when configuring a DHCPhelper address. The OUI is a 24-bit number assigned to a company or organization foruse in various network hardware products, which is a first 24 bits of a MAC address. If anOUI is specified, a DHCP relay agent will forward DHCP_DISCOVER message to aspecific DHCP server according to a specified OUI.To specify a DHCP helper address with an OUI, use the following command.Command Mode Descriptionip dhcp oui XX:XX:XX helper-address A.B.C.D InterfaceSpecifies a DHCP helper address with an OUI. Morethan one address is possible.XX:XX:XX: OUI (first 24 bits of a MAC address in theform of hexadecimal)A.B.C.D: DHCP server addressno ip dhcp oui XX:XX:XX[helper-address A.B.C.D] Deletes a specified DHCP helper address.8.6.4.2 Smart Relay Agent ForwardingNormally, a DHCP relay agent forwards DHCP_DISCOVER message to a DHCP serveronly with a primary IP address on an interface, even if there is more than one IP addresson the interface.If the smart relay agent forwarding is enabled, a DHCP relay agent will retry sendingDHCP_DISCOVER message with a secondary IP address, in case of no response fromthe DHCP server.ii
