ACI itself does not provide DHCP services for client endpoints. The only DHCP provided by the APIC is for Switches for the infra VRF & VXLAN overlay.
For endpoint DHCP you can put devices (DHCP server and Clients) in the same Bridge domain (subnet) and/or EPG and assuming you have L2 reachability, then DHCP can be provided by a DHCP server. If you need to cross L3 boundaries, you need to leverage DHCP relay. This is well documented here: https://community.cisco.com/t5/data-center-documents/technote-on-dhcp-relay-in-aci/ta-p/3161830
Robert
