In a Cisco ACI Multi-Pod deployment, the spine switches within a pod should not be directly connected to the spine switches in another pod. Instead, they should be connected to an IPN (Inter-Pod Network) device that provides Layer 3 IP connectivity between the pods. This setup allows for the extension of the ACI fabric across multiple locations while maintaining a single logical fabric. The IPN device can be a router or a switch with Layer 3 capabilities that can handle the necessary routing protocols and encapsulation methods required for Multi-Pod communication. References := Implementing Cisco Application Centric Infrastructure Official Cert Guide

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 To limit both local and remote endpoint learning to instances where the source IP address belongs to a bridge-domain subnet in the VRF instance, the action that should be taken inside the Cisco APIC is to enable the “Enforce Subnet Check” feature. This configuration ensures that IP addresses outside the configured subnets for the bridge domain are not learned, preventing mis-learning of IP addresses that do not belong to the fabric12.