Configuring DHCP Server and Relay Settings 1039discover requests typically include options for the IP address (option 50),subnet mask (option 1), default gateway (option 3), and DNS server (option6). These options are predefined.For options that are not predefined, you can enter the option code and specifythe data type along with the data that the switch should include in DHCPoffers. RFC2132 specifies many of the DHCP options. Additional options aredescribed in later RFCs.How is DHCP Option 82 Used?The Dell Networking Operating System (DNOS) supports insertion ofDHCP Option 82 information into DHCP messages relayed to DHCPservers. The Dell Networking switch can be configured to insert either theCircuit ID or the Remote ID or both. When enabled, the Circuit ID containsthe port identifier over which the DHCP request was received. The RemoteID is configurable by the administrator on a per-switch basis.Consider a network with multiple DHCP servers, where the administratorwishes to serve addresses from a specific server based on the switch and portto which the user station is connected. User traffic is served on VLAN 10 or20.The administrator globally enables DHCP relay and configures DHCP relayon the end-user ports of each switch as follows:console(config)#dhcp l2relayconsole(config)#interface range gi1/0/1-24console(config-if)#dhcp l2relayconsole(config-if)#exitThen, the administrator configures the remote-id and circuit-id:console(config)#dhcp l2relay circuit-id vlan 10,20console(config)# dhcp l2relay remote-id "Switch A" vlan 10,20Finally, the administrator configures the uplink for DHCP relay and sets theinterface to trust Option 82 information received on the interface:console(config)#dhcp l2relayconsole(config)#interface range te1/0/1console(config-if)#dhcp l2relayconsole(config-if)#dhcp l2relay trustconsole(config-if)#exit
