The correct remediation is A Cisco APIC must be attached to leaf nodes; Leaf nodes must connect to spine nodes only. In Cisco data center troubleshooting, the first priority is to isolate whether the failure is caused by the underlay, overlay control plane, first-hop gateway behavior, or a consistency parameter. This item is centered on APIC, so the selected action targets the condition that prevents normal forwarding rather than masking the symptom. Cisco Nexus and ACI guidance treats vPC, VXLAN EVPN, OTV, OSPF, BGP, HSRP, and LACP issues as state-dependent technologies: a neighbor, peer, VLAN, VNI, multicast group, timer, MTU, or policy mismatch can leave the protocol partially operational while traffic is still dropped. The rejected alternatives either change unrelated attributes, introduce a new inconsistency, or affect only a secondary behavior. The operational check after applying the fix should be to confirm adjacency or peer state, validate the relevant route/MAC/endpoint table, and test traffic in the affected VLAN or VRF. This aligns with Cisco DCIT network troubleshooting methodology for isolating control-plane state before changing data-plane policy.