Endpoint policy control consists of two logically coupled elements:

Policy repository: This is a collection of policies and rules applied to existing or hypothetical (either deleted or not yet created) endpoints.

Endpoint registry: This is a registry of endpoints currently known to the Cisco ACI. External client endpoints are any external computing, network, or storage element that is not a component of the Cisco ACI. Client endpoints are directly connected to the Cisco leaf, or indirectly through a fabric extender (FEX) or intermediate switches (such as blade switches in the blade systems) or a virtual switch. For example, a computing endpoint can be a single virtual machine’s VM network interface card (vmNIC) or virtual NIC (vNIC), a physical server connection through a physical NIC, or a virtualized vNIC (SR-IOV, Palo, etc.)