Correlating protocol data units transiting networks with differing addressing schemes

A computer-implemented method of identifying associated communications between a first network with a first addressing scheme and a second network with a second addressing scheme is presented. The technique can include: detecting a first protocol data unit addressed from a first device in the first network and addressed to a destination in the second network, prior to translation by a network address translator; inserting, prior to translation from the first addressing scheme to the second addressing scheme, a breadcrumb protocol data unit that is addressed to the second network, the breadcrumb protocol data unit including, in a location immune from address translation by the network address translator, the source address of the first protocol data unit; receiving a translated breadcrumb protocol data unit; and reporting an association of the source address of the first protocol data unit with the translated source address of the first protocol data unit.