To meet the criteria for configuring the Cisco ACI fabric to connect to vCenter, the following actions should be taken:

Create a dynamic VLAN pool with the VLAN range of 20-30: This step involves creating a VLAN pool that dynamically assigns VLANs within the specified range to the port groups as they are created1.

Create a VMM domain and associate it with the VLAN pool: The VMM domain is a representation of the VMware vSphere Distributed Switch (VDS) in ACI, and associating it with the VLAN pool allows for the automatic creation of port groups on the VDS1.

Create the EPG and associate the domain: An Endpoint Group (EPG) is a logical entity to which workloads are attached. Associating the EPG with the VMM domain ensures that the port groups are automatically created in vCenter when the EPG is associated with a VMM domain1.

Set the deployment immediacy to On Demand: Setting the deployment immediacy to ‘On Demand’ optimizes the CAM space on the leaf switches by deploying policies to leaf nodes only when endpoints assigned to this EPG are connected, rather than immediately upon configuration12.

By following these steps, the network engineer can ensure that the Cisco ACI fabric is correctly configured to connect to vCenter, with port groups being automatically created on the distributed virtual switch, using the VLAN allocation in the range between 20-30, and optimizing the CAM space on the leaf switches.