Verify the VPC connection from the Cisco ACI fabric to the Dell MX SmartFabric uplink, as shown in the following figure, that it is up and properly configured to the designated VLANs and EPGs. To do this, perform the following steps.
In the APIC UI, click Fabric > Inventory > Pod name > Leaf name > Interfaces > VPC Interfaces and scroll down to the applicable port channel VPC policy group as shown in the following figure.
Verify that the port channel protocol shows as lacp-active and that the Oper State shows as up.