receiving, at a first core network node associated with a first radio access network (RAN), a first handover request from a second core network node associated with a second RAN, the first handover request being for a first wireless device on the second RAN, the first handover request including a first cell identifier identifying a source cell site associated with the second core network node;

determining, by the first core network node, that the first cell identifier in the first handover request matches an allowed list of cell identifiers stored on the first core network node, the cell identifiers on the allowed list identifying supported source cell sites; and

accepting the first handover request.