Device for interconnection and routing between a local network enclave (E_201) and at least one transport network (T_204, T_205, T_206) comprising: first means which are suitable for selecting, for a communication flow originating from the local source network (E_201), at least one path towards the network enclave (E_203) for which it is intended and for associating this path with a marking value, means for insertion of the marking value in a header field of the packets of the flow, means for encrypting all the flow with the exception of the header fields, second means which are suitable for receiving an encrypted flow which is transmitted by the first means or which originates from another local network enclave (E_201, E_202) and switching it, without decrypting it, to the next node of the network located on the selected path, in accordance with the marking value read in the header field of the packets, a gateway for communicating to the second means the association between the marking value and the switching to be applied in accordance with the path selected by the first means of the device, the first means being further configured to: establish and maintain (312, 313) at least one connectivity graph of the overall logic topology of the network which contains all the logical links which connect the local network enclaves to each other and at least one item of information relating to the quality of transmission over the links, selecting the access path to the destination network enclave (E_203) from the information relating to quality and at least one routing constraint of the flow to be transmitted in order to comply with this constraint, communicating the path selected and the marking value associated with the first means of the other interconnection and routing devices located on the path. first means which are suitable for selecting, for a communication flow originating from the local source network (E_201), at least one path towards the network enclave (E_203) for which it is intended and for associating this path with a marking value, means for insertion of the marking value in a header field of the packets of the flow, means for encrypting all the flow with the exception of the header fields, second means which are suitable for receiving an encrypted flow which is transmitted by the first means or which originates from another local network enclave (E_201, E_202) and switching it, without decrypting it, to the next node of the network located on the selected path, in accordance with the marking value read in the header field of the packets, a gateway for communicating to the second means the association between the marking value and the switching to be applied in accordance with the path selected by the first means of the device, the first means being further configured to: establish and maintain (312, 313) at least one connectivity graph of the overall logic topology of the network which contains all the logical links which connect the local network enclaves to each other and at least one item of information relating to the quality of transmission over the links, selecting the access path to the destination network enclave (E_203) from the information relating to quality and at least one routing constraint of the flow to be transmitted in order to comply with this constraint, communicating the path selected and the marking value associated with the first means of the other interconnection and routing devices located on the path. establish and maintain (312, 313) at least one connectivity graph of the overall logic topology of the network which contains all the logical links which connect the local network enclaves to each other and at least one item of information relating to the quality of transmission over the links, selecting the access path to the destination network enclave (E_203) from the information relating to quality and at least one routing constraint of the flow to be transmitted in order to comply with this constraint, communicating the path selected and the marking value associated with the first means of the other interconnection and routing devices located on the path.