Hi @gavinhans
The answer to your question is in the vPod whitepaper:
In a physical Pod, spines and leafs participate in both the control plane and the data plane. In a Virtual Pod, vSpines and vLeafs maintain the control plane connectivity to the main data center but are not part of the data path. AVE is the data path component of the Virtual Pod and connects to the spines and border leafs in the physical ACI fabric through VXLAN tunnels.
Virtual Spines (vSpines) are responsible for extending the MP-BGP control plane from other virtual and physical Pods through peering with other Pods, spines, and vSpines. vSpines also provide a local instance of COOP used by AVE to query endpoint-location and external network reachability information in the fabric. Virtual Spines are not in the data plane and are deployed in pairs to ensure control plane redundancy.
Virtual Leafs (vLeafs) are responsible for managing the AVE discovery, and selectively push AVE configurations to each AVE based on the endpoints connected to it. In the current version of vPod, two vLeafs are deployed to ensure the redundancy of the AVE management plane in case of host failure or upgrade of vLeaf. In the future, the vLeaf tier could be scaled to cater for more AVEs per vPod. vLeaf is assigned a pool of IP addresses by the APIC to be handed out to AVEs during AVE discovery. This function is similar to physical leaf behavior in the discovery of AVEs.
Cisco ACI Virtual Edges (AVEs) are responsible for the data plane function of the vPod. One AVE is deployed per hypervisor host (workload host) that belongs to a Virtual Pod. The AVE implements full routing and switching functionality and also enforces ACI segmentation policy in the virtualization layer. The AVE communicates with vSpines using COOP protocol to exchange endpoint location and external network reachability information. The AVE receives its TEP address from the vLeaf using DHCP, similar to an AVE that is connected to a physical leaf.
Reference: https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-742393.html#VirtualPodconnectivitydeploymentcons
Regards,
Sergiu
