A data communication apparatus to be coupled to a first network and a Multiprotocol Label Switching (MPLS) network, includes a receiving unit which receives a data including header information indicating a destination and first header information used to identify a first Virtual Private Network (VPN) in the first network. The apparatus also includes a transmitter which transmits data having added thereto a MPLS header information used to identify one of the plurality of second VPNs in the MPLS network, the MPLS header information corresponding to both the header information indicating the destination and the first header information used to identify the first VPN in the first network included in the received data.