A method of testing a network comprising: (a) providing an unaddressed test device connected inline in the network , wherein the test device has one or more predefined identification patterns stored therein, and wherein the test device has memory for storing a set of collected network addresses; (b) originating a test device identification packet, at the test device wherein a source address of the test device identification packet is one from the set of collected network addresses, and wherein the test device identification packet includes one of the predefined identification patterns; wherein the test device identification packet allows the test device to be discovered in the network; (c) receiving a packet at the test device , the packet having a source and a destination address, wherein the source and the destination address identify devices different from the test device and scanning in the packet for one of the predefined identification patterns; (d) if the received packet includes none of the predefined identification patterns, adding said destination address or said source address of said packet to said set of collected network addresses, and forwarding said packet from the test device to the destination address of said packet; (e) if the received packet includes any of the predefined identification patterns identifying the packet as being a request packet sent to the test device , the packet including information targeted to the test device , the information targeted to the test device including a test parameter, in response of receiving said request packet forming a test result packet at the test device , wherein the test result packet includes one of the predefined identification patterns; and, sending the test result packet from the test device to the source address of said request packet, wherein a source address of the test result packet is one from the set of collected network addresses and identifies a first downstream device that is downstream from the test device with respect to packets originated at the device having the source address of the request packet. (a) providing an unaddressed test device connected inline in the network , wherein the test device has one or more predefined identification patterns stored therein, and wherein the test device has memory for storing a set of collected network addresses; (b) originating a test device identification packet, at the test device wherein a source address of the test device identification packet is one from the set of collected network addresses, and wherein the test device identification packet includes one of the predefined identification patterns; wherein the test device identification packet allows the test device to be discovered in the network; (c) receiving a packet at the test device , the packet having a source and a destination address, wherein the source and the destination address identify devices different from the test device and scanning in the packet for one of the predefined identification patterns; (d) if the received packet includes none of the predefined identification patterns, adding said destination address or said source address of said packet to said set of collected network addresses, and forwarding said packet from the test device to the destination address of said packet; (e) if the received packet includes any of the predefined identification patterns identifying the packet as being a request packet sent to the test device , the packet including information targeted to the test device , the information targeted to the test device including a test parameter, in response of receiving said request packet forming a test result packet at the test device , wherein the test result packet includes one of the predefined identification patterns; and, <EOS>