Which command configures a DHCP relay agent on an interface?

The ip helper-address command configures a router interface to forward specific UDP broadcast services, including DHCP (port 67 and 68), TFTP, DNS, and NetBIOS, to a specified unicast IP address. This is essential for DHCP to function across different subnets, as DHCP Discover messages are broadcasts and typically don't cross router boundaries. The router acting as a relay agent receives the broadcast, changes it to a unicast packet, and sends it to the DHCP server. ip dhcp relay is not a valid Cisco IOS command for this purpose. ip dhcp pool is used to define a range of IP addresses and other DHCP options on a router acting as a DHCP server. ip address dhcp configures an interface to obtain its IP address dynamically from a DHCP server, rather than acting as a relay.