OpenStack integration uses two separate ML2 drivers to integrate with portions of the network:
Open virtual switch (open vSwitch, or OVS) driver—You can integrate with Cisco ACI using the OVS version included with most OpenStack distributions. This example uses an OVS driver in OpenStack neutron to select a VLAN tag for network and configure the tag on an OVS port on a hypervisor when virtual machines are instantiated. This tag serves as an identifier for the Cisco ACI fabric. Cisco ACI does not require modifications to the OVS driver or the OVS itself.
Cisco APIC driver—The Cisco APIC driver transparently maps Neutron resources to the Cisco APIC application network profile configuration. The driver dynamically adds endpoint group (EPG) mappings as each virtual machine is instantiated on a network.