This specifies which physical or logical interface on the destination node, identified by cktDestNodeId, this circuit should terminate on, so together the two objects define the full remote endpoint of the PVC. An admin provisioning a cross-network circuit must set this to the interface actually configured on the far switch, or the circuit will fail to establish or land on the wrong customer-facing port. For example, setting cktDestIfIndex to 4 routes this PVC to interface 4 on the far node, and mismatching that number against what's actually provisioned there is a common cause of the destination node rejecting the circuit setup.