The continuity of cross-border health care in the European Union depends on the ability to set up shared practices with respect to patient data exchange across Member States. This flow of data must comply with demanding security, legal and interoperability requirements, as defined by the epSOS project specifications. In this paper, we describe the OpenNCP framework that offers a comprehensive set of interoperability services to enable national and regional e-Health platforms to set up cross-border health information networks compliant with epSOS, with minimal adaptation of the existing infrastructure. The OpenNCP, available as open source software, has been adopted in 10 Member States, allowing them to securely interconnect their eHealth infrastructures.